So there's no one great answer?
Playing 2v2s with my friend last night we had a game against a Z+P combo where the Toss went massssss blink stalker. I built mutas and tried to harass wherever the P wasn't while my T partner held them off, but he eventually got so many stalkers that engaging w/ mutas would have been suicidal and we couldn't hold them off with lings + my friend's bio army, so it became a base trade (which we won).
And then they accused us of maphacking. LOLZ
Next question: I've been going ling/bling/muta a lot in HotS so far, which is unfamiliar to me since I used infestors 99% of the time in WoL and almost never went ling heavy in ZvZ. I'm struggling against earlyish (8:00-11:00 maybe?) roach pushes before I have a strong muta count - suggestions?