I have an Acard 7720U SCSI to IDE bridge. This works fairly well.
The 7220U works with Zip and IDE PC Card drives in Emax without additional adapters.
I found 4 x  Acard 7722 SCSI to IDE bridges denoted as working with ATAPI devices only.
IDE Zips are listed as ATAPI in their part number.
I did some testing, and the 7722 bridge will work with the IDE-ATAPI Zip drives in a PC or the Emax.
I tested with a Zip 100 and a Zip 250.
Caveat- The bridge firmware must be updated to:
1.77a for ver 1.6 PCB
1.77b for ver 3.0 PCB (RoHS compliant)
This requires a PC with a SCSI card. I used an Adaptec 2940U2W with firmware v3.10.0.
The SCSIDE bridge boards are LVD and therefore, do not have the 50-pin connector as is present on Emax.
They must be "adapted" to the correct connector.
They do successfully boot the Emax.