I understand.
An idea (just for the fun of it):
If zp is file based, shortcut files could be used. ZP could be able to add the shortcut of a folder A in another folder B (with a little drop down menu like for "move" function). When displaying B, zp would find A's shortcut in B's bolder and display A's thumbnail in B's album.
In the administration, shortcut subalbum would appear differently : not much editable, but with a link to the original subalbum. There, a list of all its shortcuts would be displayed.
Editing the description only once, ordering the images only once and having the files only once on the FTP would, ect ... be the advantage.
Bye the way, I am a zero in php ... (talking guys often don't DO much ...) ;o)
Thank's anyway !