There’s a couple Windows apps I’m getting, and would love for this to be a stable solution. Probably won’t get Windows ZBrush, but I’d love to hear about the stability of Parallels. 
or 
I’ve used it with VMWare Fusion without a problem. ZBrush doesn’t use hardware graphics acceleration so that is not a limiting factor. Just make sure you give the virtual machine plenty of ram.
Richard
Parallels v3 and Zbrush 3.1 WIN were very stable for me. I have Parallels 4 these days, but sadly lost my 3.1 ZB temp WIN license when 3.2 came out for OSX so couldn’t tell you how 3.5 and parallels 4/5 work together.