rename to a rar and see if winrar can repair it.
otherwise, if you cannot unrar/unzip it, nothing from it is recoverable. if you have a working swf you can use a decompiler (eg, sothink) to recreate a, more or less, working fla
and in the future, save versions of your fla files so you don't ever go through this again. saving a fla (or any other file being developed) without a version appended to its name is just looking for problems.