You can assign a base texture to your highres mesh in xnormal and bake that to your lowpoly, or you can bake vertex colors from your highres as well, both are viable ways to transfer a diffuse map from highres to lowres.
Alright, thanks for the answers guys. But i was not specific enough and forgot to add something and that is, can it project vertex colors on to a flat plane. For example after polypaint in Zbrush, can i export the HP painted model, hook up a LP flat plane and render it out that way and still get diffuse colors without any…