[Peleus]

The other issue is supply and swapping your high T3 units for the ability to switch to fragile T2 units. When you mass muta the ghost / marine / tank composition can often just roll you because of your comp.

Nydus is something to try, but often not effective because they can literally land often kill it off before it pops with SCV's, and even then it's super slow unload speed makes it quite easy for your army to be trapped when the fragile worm is sniped by the responding army with only half unloaded.

Not to hijack but here is another example of what Eldrid is talking about with the hopelessness of late game ZvT beyond a certain point - http://drop.sc/95338