Wait… whoop… an interesting topic. 
Whoop whoop! 
First of all, Zombies Aren’t The Same Species As Humans.
You’re allowed to think they are, as you’re allowed to smash your head onto a boulder that has a cavemouth drawing on it. Yes, you’re gonna have a headache if you let a zombie bite you, and you’ll feel stupid afterwards.
The idea of a parasite exausting its host to its death and after goes millions and millions of years back, which is one of the bigger reasons for our extensive genetic code and such a finesse to our immune system’s definition. Nerd /off, really - you shouldn’t be able to revert the state so to say, meaning your friendly scientist stops being a zombie all of a sudden. Dead tissue, or dying tissue decomposes pretty rapidly if it lacks purpose (organism). This way, an animated carcass is a part of a blob, an ethereal lifeform that will never say “Hello!” to you passing by. It will evolve and adapt, but its mutations have nothing to do with floral or animal mutations. And until the blob ‘drops’ the host, it cannot be reinvited into life with natural processes; it cannot tap the soil, enrich plantlife, release oxygen, multiply and develop offspring, or otherwise enter the Circle of Life. Fungal lifeforms are different because they’re much more uniform and, in essence, have very little variety - fungus is a truly simple organism that requires an abundance of relatively simple nutrients to bloom and increase population. Having something “fungal” refers to entaglement with something really “exterior”, very basic, limited and shallow - so the blob cannot live with it, but it can’t get rid of it neither. I like to think about Fungal Zombies as “Fungal Coated” undead specimens.
If you could re-engeneer the blob to do anything else than what it does during the cataclysm, the result would certainly be much, much different compared to human anatomy and its role in the current ecosystem.
