They're seen as SCSI disks as they use the PPA (100MB) or IMM (250MB) Parallel-to-SCSI adaptor. I expect you'll need to recompile your kernel, but it might be worth trying a
and see if the module loads.
In the kernel you'll need SCSI support, SCSI disk support, Parallel support, Parallel_PC support and either PPA or IMM support as applicable. I've always found the dependencies end up screwed in /lib/modules/<kernel>/modules.dep so have a look at those when you've rebuilt the kernel and modprobe doesn't work. You want to have (Assuming you're on a 100MB disk) ppa.o dependent on sd.0 (SCSI disk) and parport_pc.o (pc), sd.o dependent on scsi.o (generic SCSI module), and parport_pc.o dependent on parport.o. Alternatively just sod the modules and put SCSI, SCSI disk, and parport pc in the kernel all the time, and just leave PPA support as a module so you can load and unload it for when you connect/disconnect the drive. If you put the ppa/imm code in the kernel it'll moan at boot time when it can't find the zip drive if its powered down or disconnected.
Its probably worth checking your BIOS to see if your parallel port is set for epp/ecp mode which will speed things up a lot. There is mention of support for these higher speed transfer modes somewhere in the kernel too that you'll probably wanna play with.
And the final piece of confusion: to mount a FAT formatted parallel zip disk (assuming you have no other SCSI disks) you use
mount -t vfat /dev/sda4 /someDir
I have no idea why it sees it as the forth partition when partitions 1-3 don't exist - not that this caused me a bloody nightmare in the past or anything
You can always fdisk the drive under Linux and create an ext2 partition if you want to just use it under Linux or between linux machines. Have a look into the zip tools too. They let you write protect the disks, lock the drives etc...
In the past I've aliased (in /etc/modules.conf) /dev/sda to the ppa.o module so there was no need to actively load the module before mounting the disk, its pretty nice - just plug in the drive, power it up and issue the mount command. Job done.
Hope that all makes sense!