Gridlost, hi!
It can be done, the one disadvantage is that you cannot twist the joint, like what happens when you, in rotate transpose mode, click in the middle circle of the transpose line.
But it is good for a rough pose, you should first delete all the unnecessary zpheres, leaving only the ones that represent your joints, also fit them inside your mesh as best as possible, also pose it in a lower subdiv level. Or make a NEW zsphere for the rig, the proceed to attach the “skin” to the new zsphere rig (rigging pallete).
To bind a Polymesh:
1 - Create a ZSphere skeleton that fits the model to be rigged.
2 - In the Tool >> Rigging menu, click on the Select mesh button, and in the floating window, select the mesh to Rig.
3 - Click on the Bind Mesh button to create the Skinning. Your mesh is ready to be deformed.
Tip: A good trick is to create the ZSpheres as a SubTool of the mesh you wish to rig, and when the skeleton is done, clone it and use it to bind your polymesh model.
and for more info check here --> http://www.pixologic.com/docs/index.php/ZSpheres_II
Hope this helps!
