MechaTarrasque
Hero
The real question is can you get twin spell to work on Create Unread and Animate Objects, they turn inert matter into creatures.
To confuse things Create Undead can be cast on Undead already created by Create Undead in order to maintain your control of those undead, in which case if you only are casting it on one creature, twin spell should work.
I believe that since you can cast it on 3 corpses (or 10 objects) at a time, neither is eligible for twin spell. If Create Undead was 1 corpse for a level 6 spell, 2 for level 7, ect. then you could cast twin spells on the level 6 spell, but not on the higher level versions.