Ownership of the files would likely be lost (I assume the zip file wouldn't contain that information), but it could be probably be restored by group admins on an as-needed basis.
And what about any additional text that might have been added for various photographs? I know that many "uploaders" are lazy when it comes to tidying up photographs names and adding explanatory text, but those that are diligent should not have to see their efforts come to nothing.
If any change is to be requested, IMHO it ought to be resizing in situ.
