The average true supernatural Zombie will live up to 7 years if it feeds upon human flesh regularly. The paranormal zombie virus that intertwines with human DNA transmutes cells into living dead structures somewhat akin to cancer cells. The zombification virus digests consumed human flesh into metaphysical energy. This is the energy that feeds the virus thereby slowing down the rate of cellular necrosis. If the zombie ingests little or no human flesh then it will completely decay into a skeleton within 3 years or less depending on a variety of environmental factors. Once the brain has sufficiently decayed it will cease moving. Mystical intervention by a practitioner of magic can prolong a zombies life indefinitely. Such zombies act as mindless minions to wreak havoc on behalf of these nefarious witches, warlocks, wizards, dark priests, and sorcerers.
All three of these supernatural beings are notorious for creating others of their kind via the respective paranormal viruses they carry. In a thunderous three way attack the vampire would have no effect because it’s supernatural vampire virus is only contained within it’s bloodstream. In order to create a Vampire one must be nearly drained of all human blood before ingesting vampire blood. So the battle is between the Werewolf, and the Zombie who do in fact transmit their extranormal viruses via saliva. The Werewolf, aka Lycanthrope, Virus is the strongest, and would eradicate the Zombification Virus. You would then transform into a Werewolf on the next full Moon. This is tons better than turning into a mindless cannibal composed of rotting flesh.
So if by some fluke you were simultaneously attacked by all three titans of terror, you would only become a Werewolf! Of course one would assume the vampire wouldn’t want the competition, and would proceed to eradicate the werewolf, and zombie. He or she might have to exert extra effort to take down the vampire depending on how long they lived, and what generation they are from. These factors determine a vampire’s strength. If the vampire had intentions to bring you across into the dark eternal shadows then the introduction of the vampire virus into your body would easily destroy the werewolf, and zombie virus. You would then become an immortal being who preys on humans for blood!
Many supernatural beings of evil are repelled, or even physically harmed by the holy rays of the sun. This is not the case for Zombies who are technically neutral, and not evil since they’re only acting on instinct. However this isn’t the reason they can come out during the day. The sun only has paranormally negative effects on those beings who have a certain level of demonic based DNA. This includes vampires, and werewolves. Zombies don’t have demonic DNA as they are merely living dead corpses under the power of the zombie virus.
The supernatural virus itself doesn’t have any demonic links but rather originates in magic, and alchemy commingling with dead flesh. This is also why religious artifacts like crosses, crucifixes, Bibles, Holy Water, etc. don’t work when it comes to repelling or killing zombies. Besides a few herbs that work as repellents you must eradicate zombies the hard way with brute force. Despite the zombies ability to exist in sunlight they are most often encountered at night since the glare of the solar rays impairs the vision of their less than perfect eyes. Eyes that are slowly entering a complete necrotic state as their body rots over the course of years. During the day a zombie will be drawn to the shade of foliage, caves, or human made structures. During a zombie apocalypse it makes sense to avoid wooded areas, and unsecure buildings, that provide them comforting shade.