From The Urban Dead Wiki
Zombies have access to the zombie skills tree, and can pay 100 XP for any zombie skill. Characters that begin the game as a zombie start with the skill Vigour Mortis, which gives them +10% to hit when using all non-weapon attacks.
Initially, zombies move more slowly than the living, taking 2 AP to travel from one city block to the next. This cost is reduced to 1 AP, the same as for survivors, once they purchase the Lurching Gait skill.
Because zombies are already dead, they cannot technically be killed. If a zombie is 'killed' by having their HP reduced to nothing, they will become a dead body, which will rise again in zombie form. The cost for a 'dead' zombie to rise is 1 AP if they have the skill Ankle Grab, and 10 AP if they do not possess this skill. If the zombie is killed by a survivor with the Headshot skill, it costs an additional 5 AP for them to stand up (6 AP total with Ankle Grab, 15 AP without it).
Zombies begin the game with the following attacks:
These may be progressively improved by obtaining zombie skills.
At one point, headshot had the effect of causing zombie players to lose XP; newly dead survivors started their lives as zombies with a 25% hit rate (the same as their living counterparts); more experienced zombies felt their maxed-out attacks were also somewhat weak compared to survivors' combat abilities; zombie coordination in-game was almost impossible; and in general it seemed the survivors were getting more attention in the game updates. This confluence of factors caused hundreds of zombies to go On Strike and cease playing altogether.
Since then, several new skills and tweaks have been added, making the zombie class a good choice for new or inexperienced players. Newly-dead survivors sport an equivalent hit rate to their survivor counterparts; experienced zombies can acquire Tangling Grasp to boost their combat effect; Feeding Groan helps bring zombie hordes together for community feasting; and, of course, there is nothing quite like seeing the panicked messages of fleeing survivors as they realize their comfortable safehouse is suddenly overrun with the hungry undead.
Zombies appear to always spawn Outside of any location that is within 2 blocks of a non muffled Feeding Groan.
Your eyes flick open, first one and then the other, staring blankly along the cold ground. Memories of sirens echo in your ears for a moment, and fade into strange and distant murmurs.
Unsteadily, and on awkwardly angled limbs, you rise to your feet.
This is the only class available to zombies, thus the choice is slightly limited. Originally, some zombie players would choose to start as survivors to gain access to useful skills such as Body Building before switching sides. Once the skill Flesh Rot was introduced in October 2008, zombie players were able to reach their full potential without having to become revived as a survivor at all.
Zombie players gain experience only by destroying things and harming people. As survivors tend to stay behind closed doors and barricades, and destroying barricades is a lengthy and tedious process, there are a number of things a zombie can do to aid themselves.
Most survivors have learned to stay off the streets, and most buildings are barricaded, but survivors standing on the streets should be seen as a welcome gift, and devoured immediately. This source of food is rather rare, however.
Higher level zombies can use the skill feeding groan to alert nearby zombies of the presence of survivors without protection, and low level zombies should head towards such groans whenever possible. Flares fired by survivors can also be seen at a distance and will indicate the presence of a survivor, but there is far less of a guarantee that the survivor does not have protection, if they remained there at all. In the absence of feeding groans, a flare can be a good target, but feeding groans are the best way to go.
Zombies looking for large meals should seek out Necrotech buildings, malls, and forts, since these locations possess critical survivor resources and tend to be filled with plenty of meat to devour. Since these locations tend to be heavily guarded and their barricades actively maintained, they may require metagaming organized groups to break through. Once the defenses are down, feeding groans can alert nearby feral zombies that the feast is ready.
Buildings with signs of a functioning generator (such as lights on inside, or a mobile phone mast with blinking lights) should be attacked before others, as these require active survivor attention in order to stay lit, and thus may have meat inside. Buildings with the door open and a generator working is probably in the process of being attacked by another group, and joining in on the feast will be profitable.
All in all, suburbs containing only ruined buildings will tend to have fewer survivors, but those survivors will be the easiest to catch, while barricaded and powered suburbs will have more survivors to eat, but will likely require concentrated effort by multiple zombies in order to reach any of them. Choose your feeding grounds as you would prefer.
Zombies that wish to live again must be revived by a survivor with a NecroTech syringe. This can be beneficial to a zombie after gaining extra experience, as the survivor skill NecroTech Employment will enable them to identify NecroTech buildings from the street, even as a zombie. This is the only benefit of revivification; Flesh Rot, when paired with Scent Blood, is functionally identical to Body Building, a flak jacket, and Diagnosis. However, there is no zombie skill that can replace Necrotech Employment.
Survivors wishing to become a zombie need merely die via whatever means available, be that angering a large group of survivors by attacking generators, radios, or survivors (which will entice them into attacking you), running headfirst into a large horde of zombies desiring to devour brains, or simply jumping out of the nearest tall building.