I use a G3 with an internal zip drive - my machine locked up and I had to force eject a zip disk with the magic paperclip tool. This was on a beige G3 desktop model - not the tower model - there is a little hole on the upper right that you have to get down and peer into the zip slot to see. The hole is much more obvious on the tower model. If you have a disk you can't eject for whatever reason, unfold a paperclip and stick it in that hole to eject it. Of course, this is not always a good idea, I found, as after 'force-ejecting', the zip drive would no longer recognize any disk, and the zip drive light would flash green. If you open the zip drive flap with your finger, you can see a light on the inside to the right. I ripped out all extensions, preferences, and applications with "Iomega" in the name, threw them away. Downloaded the latest Iomega software from their web site. Restarted and zapped my PRAM. I did a deep zap and let it restart 4 times - do this by shutting down the mac, then at startup hold down these 4 keys - Option Apple P R - this is known as a "vulcan nerve pinch." Keep holding them down and you will hear your mac restart. Let that happen 4 times, then let go of the keys and let it finish starting up. After I did that, I re-installed the Iomega tools software. Re-start one more time, voila, my zip is back!
Zip problem #2 - disks cannot be erased, formatted or renamed, error message says files are in use or the disk is shared. Neither is true! Solution: turn off file sharing in the control panel of the same name. Now you can reformat, rename, etc. Turn file sharing back on when you are done. This was a problem on the beige G3 and on a co-worker's blue & white G3.