Welcome and Hello;
This was a grass that I had wanted for quite a while, not only is it drought tolerant but resistant to many blights that can take their toll on all but a few. However I found out that during extended heat and drought conditions, Zoysia will enter into a 'high summers dormancy' state.
My brother in law lives in Amarillo Tx. and even with the high humidity, his gets dinged pretty good, though not to the point as yours. So I'm guessing you live in a drier climate ( it would be helpful and you'd avoid a lot of frustrating questions if you filled out your profile - upper left corner - little person icon ).
I really don't think anything BAD happened to your grass, it's actually one tough sonofabuck to kill, almost as bad as bermuda! I suggest the 'wait and see' approach.
Good Luck
