Attached Link: http://www.philc.net/forum/viewtopic.php?t=2572

 P3dO Explorer Pro will attempt to produce a view of a PZ3 file, the free version is limited to OBJs.

I make a habit of saving a render along with any scene project, even if it isn't completed yet. When I come back after an interval, it's easy to see what was in the file. Coincidentally (or not?) PhilC has just published a Python script which will save a thumbnail along with the scene.