It should be able to boot from it no problem, just put the disk in the drive *BEFORE* powering on the Mac. Most removable-disk SCSI drives will, if the disk is in when starting up, report that they are a hard disk rather than a removable-disk drive.
At least, I've used a Zip100 this way - when you do it in this order:
1. Power on Zip drive.
2. Insert disk.
3. Power on computer.
4. Computer boots from Zip disk, treating the disk as a hard drive.