The only way I know of is to edit the cr2 file in a text editor.

Another quesiton for everybody.  Is there a way of getting rid of a material zone in Poser
instead of having to edit the cr2 file in a text editor?
The grouping tool lets you create a new material zone but I haven't figured out
any way within Poser to delete that material zone if you made a mistake.
Once it is created it seems to be there forever.