Thanks for your great information about the interaction between zoysia
and nutsedge. It was very interesting.

I'm staying organic, so the Sledgehammer is out of the question in my
yard, and I've been doing the pull-thing. I've pulled tons of purple
nutsedge blades so very few are visible now, but I expect to be pulling
more blades as they regrow in coming months. Hopefully the winter will
slow the sedge down. Right now things are looking aesthetically
pleasing in the yard with the sedge not visible.

Yellow nutsedge seems to be a lot easier to eradicate by pulling than
purple nutsedge.