Back with another Q&A post, this question (#2) comes from Raoni Novellino.
"I am a Zerg platinum player. I have difficult to win games when:
1×1 games
Terran: – use early Siege Tank;
– use early Thor/SVCs and few marines/marauders;
I know that ultralisk is very effective against tank, but ultralisk is hard to do, and siege tank is very easy. 
With Mutalisk, terran player make some marines, if he scout me, it is a lost time.
Finally, the brood lord, he is very hard to do.
I know that I do not have to give player opportunity to tech to siege tank, but siege tank is very easy to do, and terran player turtles, and make siege tank, I expand, and rush for mutalisk, with 6-8 mutas, I press them, but he built towers to defend air, them I can not harass. I try tech to ultralisk or brood lord, and he outs his base with tank and MMs, and my army is not prepared yet."
This is kind of a long question, but the basic idea is, "As Zerg, how do I defend against Siege Tanks and early Thors?"
We'll start with how to defend against an early Thor with SCV's.
Defending The Early Thor w/ SCV Push
As a Zerg player you probably know that your role is largely reactionary. If your opponent never attacks you, you should expand and make tons of Drones and constantly be creating more Larvae with your Queens. Then when your opponent attacks you can make enough units all at once to fend him off and go back to making Drones.
This is much easier said than done, and takes a lot of practice for sure.
Scouting is essential. As Zerg you have the cheapest scouts especially once you have Overlord speed and Overseers. But in the early game, don't be afraid to sacrifice an Overlord to see what your Terran opponent is up to. Just plan on it dying and make another to replace it.
To defend against an early Thor you have basically two options: Roaches or Zerglings (preferably Speedlings). Roaches are awesome, especially with the range change that happened awhile ago.
If you don't want to go Roaches, just make a lot of Speedlings. An early Thor push will usually consist of 5-6 Marines, a Hellion, Thor, and some SCVs. With enough Speedlings (30ish) you'll be able to surround them and take out the force pretty easily. You may need to target fire repairing SCVs, I'm not sure if your Zerglings will do that for you.
A lot of this game is about knowing how many of your units can take out the advancing army, which mostly comes with experience.
Overcoming The Terran Siege Tanks As Zerg
It's very likely that you'll never kill the Terran player before they get Siege Tanks, they are just too easy to get out. So you're going to have to figure out a way to deal with them effectively that you're comfortable with. Here's my ideas:
One thing that you must always keep in mind when you're up against a Terran player that uses a lot of Siege Tanks is that they are VERY immobile. As soon as that Tank un-sieges it becomes much less powerful, and it takes 3 seconds to siege and un-siege. This can be fairly hard on smaller maps since Terran players can build a line of Tanks to your base relatively quickly, but on bigger maps the advantage goes to you.
If you see your opponent is making Siege Tanks and turtling you have the right idea of expanding. But expand more! There's no rule that you have to take 1 at a time. If Terran is turtling hard on 1 or 2 bases, then take 3 or 4 and he won't be able to do anything about it. Don't be afraid to lay Hatcheries down all over the place.
Secondly, you're right that Ultralisks and Brood Lords are very good against Siege Tanks and defended positions, but those units are much harder to get to like you said. So don't even think about them until the game has been going on for a long time. Take advantage of the powerful lower tier units that Zerg has: Speedlings, Roaches and Infestors.
Instead, take advantage of the immobility of the Siege Tanks and hit the opposing player where they are weak. Try some of these hit & run tactics:
- Use Nydus Worms to get your army into the back of his base, then retreat when his Tanks & army get there.
- Drop Roaches on expansions (or Banelings in a mineral line)
- Make a group of Mutalisks to poke in and destroy SCVS, Reactors, Tech Labs, Supply Depots, anything to slow him down.
- Research Tunneling Claws for your Roaches and sneak under Siege Tanks to avoid their long range.
- Send Speedling counterattacks to pressure his main base if he's attacking you
- Burrow some Infestors and lay down a bunch of Infested Marines in his mineral line
- Attack where the Tanks aren't, then move in with Zerglings and Roaches when he un-sieges his Tanks to defend.
I'm sure there's more, so be creative! The key thing here is to avoid attacking the Siege Tanks while they're sieged. Scouting with Overlords, Creep, and burrowed units is a great way to catch his army off guard while he's moving into position. And if he doesn't want to attack, just macro up and expand a lot to gain the economy advantage. Then if the game goes on long enough you can tech to Brood Lords or Ultralisks for the final push to take him out.
If you have other ideas that will help or followup questions, please leave them in the comments below!
