8/26/2013 8:08 AM
My experience with Zoysia is that is does not like extreme scalping down to dirt or any verticutting. That being said, we do scalp our Zoysia a few times each year and bag the clippings. By scalp I mean lower the height in half and do a few mowings, then raise back up 50%. So if you were at 4" with regular mowing, scalp to 2", then raise back up to 3". It can survive this no problem.
We did a test area once year and overseeded with a three-way perennial Rye. Looked fine all winter and didn't really harm the Zoysia. However, we also only put out about 4#/m of Rye, or roughly 160#/ac.
Heavy topdressing will help also, but won't do anything for the thatch other than bury it. You might find you'll have to rip it out and replace since aerifying would have to be pretty aggressive over the next few years to see any result.
Be careful to not over fertilize. Zoysia patch is a pain once you get it. Zoysia loves the minors, so apps of Iron, Mg and Mn will keep it green. In my personal experience, 3#N/m spaced out in 6 apps at about 1/2#N/m is sufficient.
In my personal yard I have Empire Zoysia. I mow at 3", scalp a few times each year, and only apply about 2.5#N/M. It's beautiful right now. Only thing I hate about it is that it dries out quicker that what I would like and requires more water to stay green during dry periods. But, if left to go dormant it won't die.