Depending on what was done to create the figure, the geometry of the figure might be completely contained within the PZ3. If this is the case, you would be selling (or distributing for free is just as bad) geometry created by Zygote. If the PZ3 file references an .obj for its geomertry (and requires it to load), you would be free to distribute it.

BTW, I'm going to go on the record here and say that I hate it when people send pz3 files instead of cr2's. Everyone uses different document window sizes and background colors and all that stuff and it's just a pain to set everything back to the way I like it. Sure, I could import, but I never think of this until its too late.

Anyway, sorry bout the mini-rant. Hope this helps.