Well the main problem with calling them "zombies" and they not being close to the core idea of "zombie" is that your first readers will likely be "zombie lovers" (sounds so wrong!!!) and they may not like what you did to their creatures which could cause bad reviews to hit the initial release of your book which could put it on weak footing for its start. An established author could pull it off much easier then a new indy of course....
Not saying do not do it just that you should understand the risk before you start. I personally stick with my recommendation that if you are going to change something, fold it in to the story/world somehow. These zombies are different because of alien dna, mad doctors potion, mutant pollen, or what ever.
Again, its your world and the key is to be consistent within your world.
