You gotta consider..
in reply to download ZIP file from web
a) are you trying to come up with a hack to be able to circumvent the mentioned problem (the site actaully points to some script or whatever that *afterwards* sends your browser the url to the file to download) in any given situation?
Then maybe just download whatever you get to a temp file- checkout the mimetype, if it's html/etc, reap it for a .zip url.
b) Or, are you trying to come up with a hack for this one site only?
Consider unix wget or curl instead. Do this in bash.