zerg units move so fast it gives them map control and they can attack so early. wall off used to work....until they come with banelings, and then their units just pour in like numberless. I can't wrestle map control with them and my record says zerg needs rebalancing.
The only one time i beat zerg was when i turtle after scouting early muta, giving up map control, set up 4 turrents with 2 widow mine to def every expansion and deny his expansion with a widow mine planted at every mineral site near him. then frustrate him enough to win.
A video to reflect the reality of HOTS TvZ