Do you use itunes? I assume not since you said zune. If you do, though, use the app DoubleTwist for Mac and Windows. If you don't use iTunes, do the fallowing:
On your HTC, download Astro File Manager
Make a new folder on the SD card called "Music"
Now, plug the phone up to a computer (any OS will do)
On the phone, make sure to hit USB Storage when prompted
Now, find where all of your music files are located on your computer
Drag and drop any music you want on the device to the Music folder on your phone
Unplug the device from the computer and open up the Music app
All of your music should be there!
If you need any help, just email me [email removed]