To be fair here, the main zerg ZvT build atm is a late expo, with quick Ling speed. The issue is Early game and Mid game terran are so good.
If Z gets to Late game and gets Ultras it's a Z win =s
Honestly, in tournament games lately I've been watching 16hatch zergs on bad positions on maps do it anyway then die 5 minutes later to reapers. I think zerg needs to experiment with getting lair tech pre-queen for roach speed, then expanding with speed roaches to stop hellion/reaper harass.