Recently I've notice that Terrans do less bioball/tank against Zerg and go for a thor heavy play.
The first problem with the mass thor push is that it's really difficult to distinguish from a standard mech play (hellions, tanks, thors) when you scout the Terran base (you just see "a lot" of factories with Techlabs on them).
The second problem is that this push often occurs before the Zerg player techs up to broodlords, which could be a pretty good counter to this.
What can Zerg do about it ?
Best Answer
As Artosis said, an army made mainly of Thors is quite immobile so you can abuse this with Mutalisks and Zerglings.