Long overdue answer...
After some more googling I found a place that made it work.
I had to add some kernel parameters, like this
changed
append initrd=/boot/i386/loader/initrd ramdisk_size=67584 splash=silent mode=5 CDBOOT=YES showopts vga=0x0314
to
append initrd=/boot/i386/loader/initrd ramdisk_size=67584 splash=silent mode=5 USBBOOT=YES showopts vga=0x0314 install=hd:/dev/sdb1 root=/dev/sdb1
Since the HDD always is /dev/sda, this will always work
Seems that the util: unetbooting is missing something like the above stuff.
I also had to move my own scripts to another place and not the "ZenWorks" usual place.
I had to move them into the ubninit (the renamed initrd) so I think unetbooting can't handle all ISOs :P
thx a lot though
Hope this will help some other dudes that needs the same stuff.
Seems that Novell ain't that keen on helping their customers with this
Now my next problem is to move this USB-bootable image to a disk and then later use that for all HDDs