What to spray on zoysia to get rid of trash.
What to Spray on Zoysia Grass to Get Rid of the Trash
If by trash you mean broad-leafed weeds, you need to use an herbicide that is specific to broad-leaf plants, and safe for grass. Here are two articles with more information: https://www.gardeningknowhow.com/plant-problems/weeds/pre-emergent-herbicides.htm
Be sue to read the labels carefully, and follow instructions exactly.