Appreciate the feedback. I was thinking the same thing, Zoysia seems to be so much more expensive on the front end, however.

Have you considered using St Augustine? Most varieties of St Augustine are mowed at the mower's highest setting and will not allow bermuda to invade. In fact I have seen St Augustine invade even hybrid bermuda and completely take over. In my own yard in San Antonio I had a spot that was alternately bermuda and St Augustine depending on the rainfall for the year. St Augustine is much less of a management hassle than bermuda.

St Augustine is a good choice but herbicides you can use are limited.

How well does zoysia resist a bermuda invasion? I would assume much better than fescue since in my area fescue can thin in the summer

I tried that experiment with zoysia and bermuda. Zoysia can be very temperamental. If it goes dormant in May due to drought, it remains dormant until the following April. During that time, bermuda easily invades and takes over.

rdaystrom is correct in that the safe herbicides are not the same as the safe herbicides for most other grasses. However, the one that works best on St Aug is extremely effective. For example one application of an herbicide with Atrazine will take out poa annua forever, seeds and all. Same with horse herb, a very pesky plant in my area. Here's the atrazine product I can find most everywhere, but there are others.