The Newly Dead Zombie units can be increased beyond their starting size by spells and effects that add models to an existing unit. In addition, when Zombie units are successfully targeted by the Invocation of Nehek spell from the Lore of the Vampires, they regain an extra D6 Wounds. However, they also suffer one more casualty than normal as a result of Unstable.
Undead All units with Undead have Animated Construct, Fear, and Unstable. However, they may make march moves if they are within 12" of the army's General.