Zombies have several differences from humans. They possess most symptoms of death with a few add-ins of life.
This is generally the reason zombies are discolored, or pale. This symptom is one of the less noticeable difference between the dead and the living, since a person can achieve that deathly color by undergoing deep shock, like the fact that the dead have come to eat the living.
A more pronounced version of Pallor Mortis, this is a corpse turns due to settling of blood. This usually occurs 6-12 hours after death, so it may not be present in newly reanimated individuals.
Algor Mortis causes corpses to drop their body temperature.
Probably our best friend, Rigor Mortis causes stiffening in the corpse, so it would be difficult to move or manipulate the corpse. This is why zombies tend to walk/run slowly and prevents them from preforming some actions such as climbing or picking up objects. However, this only applies to corpses who have already been dead for 3-4 hours, if reanimation occurs before this period is reached, the zombie may be as quick as a normal human.
This system pumps blood to and from the body. Since zombies are dead, they would not need to pump blood, which results in all four mortises and the loss of the need for a stable heart.
This system consists of the skin, hair, fat and nails. The hair should be disregarded, since it doesn't affect life or death. Zombies are skinny, since they convert their fat to energy. The skin starts decomposing and the nails stop growing, which is helpful and would prevent scratch-related attacks.
However, the skin dries up and retracts which makes the hair and nails appear longer.
This system deals with bones, cartilage, ligaments and tendons.This is what keeps the corpse from melting into one big mass of decomposing flesh. The human body has evolved to withstand most damage, but a zombie's partially decomposed appendage should be easy enough to break off without much effort.
Your real target would be the skull. It has evolved to the dome shape that we have today for maximum pain absorption and is thicker than all your other bones, so it is difficult to destroy without a proper weapon.
Zombies don't have an effective digestive system because of the lack of enzymes and a lack of a means to deliver digested food into the body systems, which is why zombies are always hungry. because they cannot digest food, their stomachs tend to bloat.
This system involves the organs used for breathing. Zombies don't breathe so they don't have a use for this system.
Due to rigor mortis, the muscles stiffen and thus the undead are cursed with the inability to move quickly.
By far the zombie's most important organ system, the nervous system is in charge of collecting, transferring and processing information with brain, spinal cord and peripheral nervous system. This system is reduced to basic movements and feeding, because only the brain stem is reactivated after death.