This drops from Zul'Jin in Zul'Aman (The lvl 70 10-man raid instance).  Their is Zul'Aman (ZA) for lvl 70 players, and Zul'Grub (ZG) for lvl 60 players.  Zin'Rokh, Destroyer of the world and Jin'Rohk, The Great Apocalypse look the exact same (Just reshaded), and each drop from the boss of each raid instance (ZG - 25-man, ZA - 10-man), so don't get them mixed up!