Zoysia does fine in Clay, you just need to aerate and lime.
They really don’t. They distress the crap grass. Will also turn Bermuda yellow. I still get big patches also crab grass in my zoysia even though it’s as thick as carpet. That stuff takes multiple applications and will weaken CG so hopefully the other grass can out compete.
Yep, preemergent works best on crab grass. I haven't had a problem with fescue, and crab grass killer. Bermuda is a weed in middle Tn. Some of that is caused by seed blends used on public road construction and repair. I've seen Bermuda runners 6 feet long.
I have never wanted zoysia because of the brown winters, but it does a better job of choking out weeds.