OP:
Is the SCSI ZIP drive you have the original 100mb version, or the later 250gb version?
I can speak only for the ZIP100 drive, which I have.
Don't waste any time or money trying to kludge the SCSI version to work with what you have.
Instead, look for a USB version of the ZIP100. You may be able to find one on ebay (or elsewhere) in good working used condition. For not very much money, probably $10-15.
I actually found a USB ZIP100 in the computer recycling bin at the local waste disposal place a while back. It looked like it had never been used! The "factory plastic" was still on the face of the drive.
Took it home, plugged it in, and... it worked!
Again, this was a ZIP100 drive -- not sure what solution exists for the higher-capacity ZIP drives Iomega introduced later on.
TIP:
I suggest you do things this way:
1. Power down, all the way off
2. Connect USB ZIP drive
3. Apply power to ZIP drive and insert disk, let it begin to spin
4. Press the Mac's power-on button
5. At boot, the OS will "scan the bus" and try to load disk drivers "where found"
6. Every ZIP disk has an "on disk driver". The OS should "find and load" this
7. Once loaded, that disk can be ejected, others mounted, etc.
(this may not even be necessary, but worth knowing)