I have tried to download mp3 files on my blackberry from website such as zshare etc... and I get an error message everytime i know I could do it on my pocket pc, can you not download mp3s via bb?
never been on zshare, but most likely you will need to convert the files to a format compatible with the BB. try using the media manager that came with the BB to convert the files, or go online and download a converter that can do it for you. For videos, I use the Ultra 3GP video converter. I dont know if it will do mp3's also, but it works great for videos.