If you still have Marathon growing in the shade, leave that alone and install UC Verde in the sunny areas. Let the two mingle through the transition from shade to sun. If you find the Marathon fading out on you, then you can use a zoysia in the shade.

My problem with zoysia is that if something happens to it (drought, insects, disease), then it's gone for the rest of the growing season until April of the following year. Here's a picture to show what I mean.

There is a low path running from the house to the street through the middle of the bed and to the curb. We had had an excessively rainy few weeks, so the water never really stopped flowing through that dead area. A fungal disease got started and knocked back the zoysia. The picture was taken in July 2013, and the grass remained brown until the following April. I had the same thing happen where I tried some zoysia. It's been many years, so these folks have figured out a solution (no, I don't know what they did). But had that been bermuda or St Augustine, they could have recovered in the same season and not had to endure the brown grass for so long.

There are too many varieties of zoysia for me to keep up with. If I were to pick on for my yard, I'd find an installation in my neighborhood and ask where they got their sod and use that. As it happens, the house we bought in 2022 came with some very hardy zoysia, that my wife has been trying to eradicate. We are having problems with our St Augustine in the front, so I'm about to propose patching in some of the happy zoysia and see what happens.

As for buying UC Verde plugs, no longer is there only one source for the plugs, so the price is coming down.

Thanks dchall, I've always respected your recommendations for grass on various online forums throughout the years. You've really been the guiding light for folks in a sea of noise and nonsense.

As for mixing UC Verde with Marathon, you don't think it'll look spotty during the winter when the fescue is green and the buffalo is dormant?

Well, there is that. If you want something that goes dormant along with the buffalo grass, then St Augustine is the only shade tolerant and heat resistant grass. There is a fine bladed variety of St Aug which is supposed to look better with bermuda and other fine bladed grasses. I don't recall that variety name and finding a source for it might be a problem. If you try to mix St Aug and buffalo I would think the St Aug would dominate given enough water. I wish I was more familiar with UC Verde, but I've never seen it in person.