I tested it now,in order to start the BF2 editor, you dont need to unpack anything.You need to have "content" folder inside Predit with zips.Just copy all files from \mods\pr\content to \mods\pr_edit\content and try to start PR_edit mode.Later if you want to work with something, then you unpack.
or that you would not take a lot of space on HD,just copy
http://prntscr.com/lju37i
this files from \mods\pr\content to \mods\pr_edit\ content