Scott is right to point to the B12@ resistances and invulnerabilities; these would be present in most undead. If your undead are magical, then you would use M1@6 protections and resistances to achieve the same result, and there's no reason you can't stack these. (Mag protections against Mag are M1@9.)
Psionic zombies tend to be P4@6 telekinetic puppets, but you can do them better as a P14@6 Animate Ojbect enhanced by a P14@9 Instill Life Characteristics. Such animated creations become unliving life forms, and thus have bod skills.
Creating the magic versions is generally a M13@8 Animate Dead skill, which turns a body into a pseudo-life form. That particular version of the skill gives the creatures a base dangerous damage category on body-based attacks, but that's not a necessary factor, only a useful one, as it enables you to create powerful attacks without relying on martial arts or high strike values.
Tech zombies can be created in scores of ways, including mind/machine implants, genetically engineered mutagenic virii, and chemical control. Most of the cases of tech zombies are not undead in any traditional sense, but are living humans deprived of control over themselves and subjected to disease symptoms that cause visible decay. However, it is not impossible to devise a technology that animates a corpse, for which nanobots are probably the simplest approach. The Borg in their original incarnation are modeled as a kind of tech zombie, something like a cyborg but controlled and individually mindless. Later borg became more independent.
In bod terms, this would be a type of symbiont, probably a B14@6 Controlling Total Body Linking, in which the parasite/symbiont connects to the host and takes control of the body. It could be anything from a genetically engineered (Tech) mutagenic virus to a naturally-occurring alien life form. Since the symbiont is able to control motor function without tapping pain response, it gives the zombie effect. It is thus contagious, by whatever method the parasite uses to reproduce.
Communicability in a mag zombie is achieved either by giving the zombie the power of animation of undead or by making the zombie a material component in the spell as cast by its caster. That's a very elaborate spell, but if you put enough into it you can negate the need of the caster to be knowledgeable or involved in the spread of the effect. Modern zombies have no caster, and thus no master, because they are usually tech/bod based.
Moan - They summon the horde by moaning. Is this Bod, or some 0@0 Psi Language variant?
Really up to you. It could be reduced to a B0@2 Signal Generation, or it could be considered a P0@0 language. It might depend on what else you want the creature to be able to do. Language generally suggests the ability to communicate concepts and information; signal generation is necessary for language, but on its own it communicates only basic survival messages: food, danger, territory. Birdsong is signal generation, as is the "dance" of bees, which is probably as elaborate as such signals can get. But summoning the horde is probably simple signal generation, assuming it's nothing more than that the others come if they hear it.
Claw - Primitive and unskilled, but bugger all strong.
Mentioned above in the mag section, but if you're going for tech/bod you want this to be a B7@3 Intensified Damage attack. (This also suggests that you can incorporate some martial arts base values in the protection of zombies. One justification for defensive sit-mods is that the defender absorbs the damage in less vital areas, which is something at which zombies could be particularly potent, not having many vital areas.) The transmission of the parasite would itself by a B7@7 special damage, and the defender would use a resistance roll against it.
Tirelessness - They never experience fatigue, thirst, or actual hunger, and cannot starve, drown, or suffocate.
Some of these are already mentioned as Bod 12@ resistances/invulnerabilities. Others might be high-level B10@ regeneration and self-healing skills or 11@ immunities.
Your real problem is that you need to cover things like
but a pickaxe to the face is more or less an autokill.
In play I would cover this by asserting that the really incredibly damaging fatal shots "happened" to connect with the head, but if anyone attempts to attack the head specifically they have to take a size penalty for a targeted shot (with a tiered possibility of reduced damage if it falls in the second category). You might consider whether successful aimed shots at the head get a damage category bonus or rider as part of the creature description, identifying a weak spot.
Which raises another question I've been wanting to ask: How does Multiverser handle things like, for instance, air elementals, or sand golems, or the T-1000, which theoretically have nothing in Density, but are in fact horrendously difficult to harm specifically because they are so diffuse?
Scott already addressed this quite effectively, and I would add only a few points.
The body parting is definitely part of the package, along with the invulnerabilities. (Remember that in Multiverser "invulnerability" means that the attack did not hurt you if you made the invulnerability skill roll successfully. Thus it is possible to harm these beings, but very difficult.) The air elemental and sand golem would also have magical protections, and the sand golem and T-1000 probably also have regenerative ability--if you can keep it from putting itself back together, it is still at full damage, and it takes time to restore itself to full functionality. I also agree that the density of a T-1000 is relatively high, and think that the sand golem is also of a relatively high density (not as high, but it is made of stone).
I hope this helps.
--M. J. Young
