This may be a little bit of topic drift, but I can't resist.
A friend and I, on discussing zombies, have decided that there are actually two distinct types of zombie. I suspect that it depends on whether you are asking about a necromantic zombie, or a hoodoo zombie.
The hoodoo zombie is technically not an undead, but brain damaged to the point of easily being controlled by its master. This brain damage also tricks the soul into leaving the body, and thus creating the status of the zombie. Hoodoo Zombies would still have to eat for biological reasons. I don’t think that for the hoodoo zombie, the type of protein they consume really matters, therefore the intelligence of the victim, I mean dinner, does not matter as well. For more reference on the hoodoo zombie see the classic documentary “The Serpent and the Rainbow” (director Wes Craven, 1987) or the textbook of the same title written by Wade Davis.
The hoodoo Zombie differs from the necromantic zombie in its method of creation, and its biological state. The soul is driven out of the hoodoo zombie, but the body is still alive. The classical zombie of the Western World is the necromantic zombie, or “undead” zombie. With the necromantic zombie the corpse is dead, and inhabited, or at least under the direct control of a malevolent spirit/entity/ or a living master of necromancy. These zombies are not biologically alive, and so do not “need” to eat. They often do though, just out of spite for the living. These zombies may conceivably seek out the best target to strike against our oppressive, life centric society. Thus they may selectively try to eat the “cream of the living”, so to speak. The necromantic zombie is the one that would select its victim based on the victim’s positive value to society. They would leave a drunk in the gutter alone in favor of eating a doctor for example.
For a reference to the necromantic zombie, I would recommend the series of movies collectively referred to as “those dumb Evil dead movies” (see “Evil Dead”, director Sam Raimi, 1981)