Definitely love Zbrush. It allows organic shapes/details that I cannot even touch with rhino. I have successfully imported 20+ MB mesh files from Zbrush to rhinocam, and the the code generated machined just fine.
I have never heard of any cam software that was able to generate toolpaths from displacement maps. There are programs for machining photographs that work from greyscale (same thing?), but I have not heard of toolpaths from surfaces w/ displacement maps. Perhaps someone with a broader CAM experience base can chime in here.