There are two varieties of these infected dogs, and while both have been created from the same species of Doberman, their origins are distinct.
The code name given by Umbrella to the B.O.W created by infecting a Doberman. The researches who created it gave it the codename MA-39. The Cerberus is extremely violent and agile. It has decaying skin, increased jumping range, endurance and aggressiveness due to its exposure to the T virus . This variety is encountered in the Arklay mountains research facility and the Spencer Mansion in Resident Evil 0 and 1, respectively.
The distinction between the zombie dog and the Cerberus is that while the Cerberus is an intentionally created B.O.W, the zombie dogs were created accidentally. The police dogs in the Raccoon City police department were infected when they ate contaminated food, and the zombie dogs encountered on Rockfort island were created in a similar manner. The police dogs retained some of their prior training post infection, making them very dangerous.