Nope. Zombies are re-animated corpses. Guardians aren't zombies. In fact, if you die and respawn too quickly, you'll sometimes find yourself standing over your own dead body in the game. Guardians are created from the fact that Einstein's Theory of Relativity tells us that Matter is just a very dense form of Energy (E=mc^2). So all that our Ghosts are doing when they "resurrect us" is to gather energy and use it to re-create a new body for us. The memory and skills part....though....is magic.

No they are not zombies.