It said playing: 4 Kb/second, which is quite a slow bitrate, maybe they're compressing people's music even more to keep their bandwidth usage down, try another host.
Not sure what you mean, but they haven't changed it to a zip file, when you compress an MP3 file you get options for the bitrate you want to use (higher bitrate = better quality but uses more bandwidth) it looks like that website has taken your file and compressed it even more.

In case that wasn't what you meant, if you want to zip something just dl a demo of Winzip or something.