I'm absolutely sure that you understand that zombies are simply mythological cultural creations & don't actually exist.
Belief in zombies exist though.
Being a big fan of all things twisted and disturbing, I read the Serpent & the Rainbow when I was a kid shortly after the movie came out. (as usual, the movie sucked in comparison to the book)
Anyway, the book came about because the author was sent to Haiti by a pharmaceutical company to research the possible medical uses of some of the ingredients. (the concoction that voodoo witchdoctors use is a combo of much more than just puffer poison but also frogs, lizards, spiders...all sorts of stuff. (dust from crushed baby skulls is my personal favorite)
Being the geek I am & always fascinated by it, about 5 years later when I met a married couple in my apartment complex who practiced vodoun, I learned during my time with them that everything I knew about voodoo was wrong.
I digress though...my point is, something in the mix supposedly allows for complete awareness coupled with complete temporary paralysis coupled with a low heart rate that appears like death to most.
People are aware they are being buried alive.
It ain't the zombinol that zombifies the victim, it's the victims belief in the powers of the witchdoctor that does it. When removed from the priest's influence, the "zombie" recovers.