Q.grass
We are in central Texas, planted a St. Augustine lawn by sod early this year but it’s performing poorly in spots all over, as well as in the shadier area. We had a good stand of St. Augustine for a few years but it got drowned last year, it’s been another wet spring and even the new lawn doesn’t seem to like the very heavy rain. I was wondering if inserted Zoysia sprigs in the poor spots and in the shady areas, if it would grow together well. I realize the blades look different -our main interest is generally soil erosion and an overall look of a green lawn. The winter temps can get into the 20s but usually not for long periods and often stays around the freezing mark. It can get well into the 90s during the summer and we can have periods of drought but we do have the ability to water if needed.

I would suggest checking with your County Extension Office. They should be able to suggest the best seed or plugs to use given the current weather trends and conditions in your region.
Here are some links for you.
https://www.gardeningknowhow.com/extension-search/