...Or any other 3rd party library.
In fact, you don't need any 3rd party library at all since Windows XP and Vista already support ZIP files. So you can make an (un)zipper without any 3rd party stuff.
Microsoft calls it "compressed folders" (which is indeed what a zip file actually is, it is a folder with one or more files and/or subdirectories), so you might wanna search for that in the
MSDN library (you'll find examples and very detailed info).
For an unzip example see:
CookieRevised's reply to [Suggestion] Skin Updater.
Zipping is very similar and many (Javascript/JScript) example codes can be found on the net.
/ 
