While most media file types are compressed in one form or another they do not usually possess a .zip file extension. So either you have some bad file association thing going on or someone did actually use a compression archiver to compress them even further perhaps for portability on a small device or emailing or something.
If they are in fact zip files you will need to use something like 7zip, winzip or the native extractor in windows 8 to get them back to their actual media format which could be any number of file extension depending on the nature of the file but not likely in any case to be zip.
Additionally you may want to save yourself some headaches and heartaches in the long run by just installing something like VLC VideoLAN - Official page for VLC media player, the Open Source video framework!
PS> Maybe open up File Explorer click the View Tab and in the Ribbon select the Options Icon drop down Change folder and Search Options...
Again select the view tab from the resultant dialog box and uncheck "Hide extensions for known file types" click OK and see if you can determine the actual file extension now and perhaps consider using "Details" view as that might provide some additional information regarding the file bit rate, size, length, artist, etc., etc., etc.