He called himself Dr Death and he conferred upon himself a doctorate in the study of zombies. He was then fully aware of the prohibition against zombie on zombie violence when he violated his first zombie. Dr Death thought the the Zombie Apocalypse was the perfect excuse to work on perfecting mankind. The only problem was that zombies ate people who were perfectly healthy. What was needed was a change. The zombies needed to eat sick people and leave healthy folks alone. This would mean that zombies would eat each other but that part couldn't be helped. When Dr Death's rain of terror was complete he was certain that the rain of error--the original Zombie Apocalypse--would be perfected. The first wave of zombies he dispatched sought out hospitals and everyone who was not healthy. While the sick eating zombies where about their father's business Dr Death perfected the second wave of zombies. The second wave would detect genetic anomalies and promptly eat anyone who had them.
The third wave would take a little AI to make sure they found the correct victims. The third wave attacked anyone who wore glasses, or carried a cane, or had an ear piece or who had contact lenses or a toupee or even a wig. A fake leg would get you eaten by third wave zombies.
Only the uninjured and the genetically perfect were left to repopulate the earth. The final zombies left ate each other. Before that happened, Dr Death left his laboratory and let the zombies feast upon him. He wore glasses, had a congenital heart defect and had even more problems that he did not care to think about.