Hi
Have another SLE or openSUSE system around, install imagewriter and use that..... AFAIK is a isohydrid so just dd should work.

Code:
fdisk -l SLE-12-SP3-Server-DVD-x86_64-GM-DVD1.iso

Disk SLE-12-SP3-Server-DVD-x86_64-GM-DVD1.iso: 3.59 GiB, 3836739584 bytes, 7493632 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: dos
Disk identifier: 0x1285b34e

Device                                    Boot Start     End Sectors  Size Id Type
SLE-12-SP3-Server-DVD-x86_64-GM-DVD1.iso1       2608   10799    8192    4M ef EFI (FAT-12/16/32)
SLE-12-SP3-Server-DVD-x86_64-GM-DVD1.iso2 *    10800 7493631 7482832  3.6G 17 Hidden HPFS/NTFS