Early game ZvP is all about getting your economy online. Generally, you are going to want to start off an with a fast expansion at seventeen drones and follow up with a third base pretty quickly as well. Of course, you will need zergling speed, queens for both of your bases in order to get injects and some spare queens for creep spreading and early defense as well. Getting creep connected between your bases is an immediate priority in order to better hold off any early game aggression Usually, the protoss player will also go for a fast expand, which is why you respond by getting a fast third base. In the early game, you should expect a fast oracle and/or some adept pressure. Stargate openers are extremely common because they are such a powerful build, so unless you specifically scout a robo opening you will generally want to throw down some blind spores at around the 3:30 mark. A single queen alone cannot really fight off an oracle at least not before your economy is totally trashed.
If your opponent does open with a robo then they will have the option of doing some warp prism play or even an early immortal timing or they could simply tech up to colossus and prepare for a later game, so be sure to keep an eye on what sort of units and buildings they have. You also want to maintain map presence with your zerglings early on. You can use a small task force of lings to deny your opponent’s third and force them to keep troops at home defensively, as well as to gain information about their army composition or what sort of strategy they might employ into the middle game.
You don’t really want to rush a lair too early, unless you want to try to an aggressive nydus all in play which can be effective, but for the most part you want to pump drones, make a few extra queens and some lings for map presence and focus on getting an economic advantage while preparing to counter whatever your opponent starts off with. Your goal is to get into the mid game on a very strong economy and then pump a massive amount of hydras, lings and banelings and try and deny your opponent’s fourth base and cementing your economic lead.
Make sure to stay proactive in fending off any adepts that do want to poke in and shave off a few drones, and always be scouting. Upgrading overlord speed can be a good way to keep tabs on your opponent. You do want to try and see what they are planning toward the midgame. For example, they might skip a third base or even make a fake third base in order to throw you off and try a massive early game gateway all in. If you have been producing nothing but drones this will probably be game over, so keeping an eye on their production facilities can help you recognize that this is coming and get you started on that safety roach production right away. If you can skip the roach warren and get straight to hydras, great, but often you will need at least a few safety roaches to fight off archon harass or the aforementioned mass gateway all in.
Protoss isn’t the only race that can go in. An early roach / ravager attack can be devastating if your opponent has been doing a greedy build in preparation for the late game. Good micro management is very important in order to maximize your chances of dealing a crippling blow to your opponent’s economy, and it is very important that your opponent not scout this attack. Rotate wounded roaches to the back of your army or morph them into ravagers to prolong their effectiveness and remember when you do an early all in like this the clock is ticking and you need to get damage done asap. Researching burrow and tunneling claws as well as roach speed can be another way to get more value out of this early aggression.
Another powerful all in play is to go up to three bases then cut drone production and simply pump a massive amount of hydras. With any luck you will be able to shut down your opponent’s third base and do a lot of damage by just over powering them with hydralisks before they have a chance to develop area of effect damage like psy storm or upgrades colossi.
The midgame for Zerg vs Protoss is all about hydra/ling/bane. If you are taking a laid back, power up drones and macro approach then getting double evolution chambers and securing those vital upgrades as quickly as possible will be very beneficial. You are taking a bit of a risk here because if your opponent is planning a massive early on attack then you would rather these resources be directed towards units that have more utility in the short term, but over the course of a longer game an upgrade advantage is going to be worth its weight in gold. Your opponent will almost certainly opt for templar or colossus tech, or even both, and it is important to develop a plan for combating these higher tech units. Colossi can be abducted by vipers and pulled into your hydra mass and storms can be dodged so you do have some options here. You shouldn’t feel the need to rush up to hive too quickly if it comes at the expense of securing your fourth or fifth base and getting a solid army to fight over the center of the map but eventually you must reach the top of your tech tree in order to stay competitive.
In terms of engaging your opponent, you want to fight on creep wherever possible, and you will need to continue spreading creep through the entire game as well as using your queens to replace any creep that is torn up by your opponent. With zerg it is crucial to hit from several different angles at once and avoid any choke points that will bottle up your units. You simply cannot afford to take bad fights, and rather than engage in an unadvantageous position you will want to make a tactical retreat so that you can fight in open terrain and/or on creep.
Baneling drops and zergling run bys are cost-effective ways of slowing down your opponent’s economy in the mid game and you will often be able to force a cancel or do some severe economic damage with these tactics. Nydus harass is another good way to put some pressure on your opponent and pull their forces out of position.
Lurkers are a natural evolution from hydras and can make a nice addition to your army composition especially since the new patch. These units are very effective at zoning out your opponents army especially if you use your hydralisks to focus down their observers. Make sure to spread out your lurkers for maximum effectiveness and be careful that they do not get caught by the protoss forces while they are in transit.
You can also a midgame tech switch to keep your opponent on their toes. For example, if you end up wiping out most of your opponent’s anti-air then a quick switch into mutalisks might catch them off guard. Mutas aren’t really a long-term solution because they have some pretty hard counters but if you catch your opponent off guard without a lot of anti-air you can do some serious damage before they can react.
Your endgame in ZvP is to add broodlords and vipers to your hydra composition. Hydras provide excellent support to brood lords and brood lords destroy pretty much any ground composition so long as they are supported. Ultralisks are not really as useful in ZvP as they are in ZvT but they do have some utility to tank damage and can even be used for runbys along with a few zerglings. The adrenal upgrade can transform your zerglings into ferocious killing machines so definitely do not skimp on it once you reach hive tech.
Make sure to keep an eye out for zealot run bys. By the time the late game arrives your opponent is going to have a ton of gateways and will be able to warp in a ton of upgraded zealots in moments, and these units will just tear through any morphing hatchery or defensive structures like they are made of butter. Strategic placement of overlords throughout the map can ensure that you are able to react in time to these attacks. Once you reach 200/200 you can become even more efficient by using static defense in addition to your army, creating masses of sunkens and spore crawlers to defend your peripheral expansions and to hold the center the map.
If your opponent does go for the golden armada composition of carriers, void rays and mothership into the late game, corrupters will handle the carriers pretty well, and you can use infestors and vipers to mind control and abduct these high value enemy units. Make sure to focus fire your units on the enemy ships themselves instead of fighting the interceptors. You will also want to sacrifice any lings and ultras you have on run buys in order to free up supply. Abducting units into fields of spore crawlers is a great way to shave off some of your opponent’s supply and win the war of cost efficiency which is ever so important in the late game.
Keep an eye on your economy. Actually in the late game you don’t mind if you end up losing a few drones, because once you are maxed out building up a bank is nice but getting an even stronger army composition is even nicer. You don’t necessarily want to sacrifice any drones, but you can build static defense or fail to replenish drones that are picked off in run bys.
Often as zerg if you are ahead you will be able to build up a massive bank while you are trying to pick a good fight against the protoss army. If this is the case then you will often have a big opportunity after a massive engagement in that you will be able to re-max your supply much quicker than your opponent. This remaxing period is a great opportunity to do a tech switch and counter whatever is left of your opponent’s units. You can also keep your options open by getting both ground and air upgrades, as well as upgrades for both melee and missile ground units. Make sure to stay on top of your injects at all of your bases as well so that you have an almost unlimited amount of larva as well as the bank to spawn it.