[npc=53023] gives 3 quests for ZG:
Break Their Spirits
Secondary Targets
The Beasts Within
When you enter the instance, chances are that she will randomly offer you one or two of the quests but not all three. This problem had me scratching my head for a while, as I've never seen this behavior before in a WoW dungeon. It has nothing to do with quest order/prequisites, weekly quests, daily heroic lockouts, or bugged UI's.
The solution is simply to go inside the dungeon's entrance solo, and if she doesn't give you all three quests, then go outside, click your player frame, and click "reset all instances". Go back in and see if she gives you whatever you're missing. If she doesn't, go back out and repeat. She will eventually offer all three, though it might take several resets. I tried this strategy on two different characters and it worked on both.
Be aware that you can only enter 5 instances per hour before you get the "You have entered too many instances recently" message from the server.