I had a zone stuck in shutting_down state.
No matter what I did I was not able to shut it down.
But this worked.
# ps -fz myzone
UID PID PPID C STIME TTY TIME CMD
root 2850 1 0 Jul 22 ? 0:00 zsched
0040620 18081 1 0 - ? 2529:10 defunct
The problem was that I had a process on the zone that was defunct.
After several kill -9 the defunct process finally died and my zones shutdown and rebooted.
NOTE: YOU SHOULD NOT KILL zsched.