ZvX 3 Hatch Speedling Build
15 Expand with Hatchery
16 Spawning Pool
26 Zergling Speed
27 Expand Again with Hatchery
27 Overlord, Queen
@7:00 Roach Warren
@7:15 Extractor, Lair
*The numbers on the left indicate the timings based on either how many drones you have built or at what time you should think about performing the next step.
The 3 Hatch Speedling build order is a safe, standard build in HOTS. It allows you to take advantage of fast Zerglings during the early game to pressure your opponent and poke slower units, especially that of the Protoss. Since this build pushes for a third expansion early, it is based on economy and can be threatened by early rushes. As such, you’re going to want to scout early and often to see if the opponent is going for early aggression. If the enemy doesn't pressure you enough, you’ll head into the mid-game with creep expanding throughout the map, and the resources to supply a powerful army.
Once you’ve reached the 7:15 mark you’re going to want to react to whatever the opponent is doing. If they’re susceptible to air, spawning a group of Mutalisks to float around the map is a great choice. However, the current standard is to build Roaches and Hydralisks. Roaches are still the most well-balanced ground unit, and Hydralisks have been buffed so they are more than just an anti-air solution for your army. Once you build a Hive you will want to think about spawning 2-4 Vipers so you can pull threatening units into the middle of your swarm (i.e. Colossi, Thors, etc.)
Lastly, don't forget to continually spread your creep. This build offers one Queen for each of your three bases so you can constantly deploy creep. If your opponent doesn't do a good job of scouting and denying your expansion, you'll have a significant advantage with overwhelming map control. Meanwhile, you can continue to send out groups of Zerglings to annoy enemy expansions that aren't fortified, particularly third expansions.