It's easier to create zombies – just resurrect them, and that's it. But in Heroes 6, ghouls were described as the souls of murderers that necromancers stuffed into corpses, and it's more difficult to control a creature with a soul.
In theory, yes. But in practice, who needs to resurrect zombies, let alone raise them? They're only useful for having 2 zombies with decent defense and attack stand around, protecting the main troops.
