There is no direct way to mount an ISO image onto a Solaris Zone. However, you can mount an ISO image onto the global zone (the server which hosts the zone) and then present it onto the guest zone.
Attach a Block Device
sunsolaris# lofiadm -a /export/software/iso_image.iso
Mount the ISO Image block device
sunsolaris# mount -F hsfs -o ro /dev/lofi/1 /mnt
Mount the mounted ISO image to the Guest zone
sunsolaris# mount -F lofs /mnt /zones/myzone/root/mnt
Where /zones/myzone/root is the root of the Zone. The files should now be visible under /mnt on the guest zone.