Rabbit Types with Disguise

I would like to disguise my zombie pigman as a white rabbit, but I can't seem to do it..
I've got:

Rabbit:
Type: PIG_ZOMBIE
Display: '&aHungry Bunny &7[Lv. 2]'
Health: 30
Options:
PreventOtherDrops: true
PreventRandomEquipment: true
AlwaysShowName: true
Disguise:
Type: Rabbit
RabbitType: White