I used SCSI Zip 100s with my Amiga 500s using a GVP A500+ HD8 and a GVP A530 Turbo. I had to set up a MountList, but other than that I had no problems. Later I used an internal Zip 100 SCSI in my Amiga 4000 with the WarpEngine 4040 and then CyberStorm MK-III. Now I have USB on my 4000, I can use Zip 100, 250, and 750, all tested and working.
In theory, I would suspect you can use an internal Zip IDE in your A500 with the appropriate IDE interface (like an AdIDE.)
