I'm still insisting that the FIRST evolution was the Zombie and the second was the Ghoul.
Because regardless of what was said, what was described and shown was Zombie for the first and Ghoul for the second.
I mean it is downright stupid how much his second evolution exactly matches the typical description of a Ghoul, while the first more closely (but not perfectly) matches the usual form of a Zombie.
That is to say a Zombie is an animated corpse, usually rotting because there is nothing in place to stop it doing so. Like a Skeleton but with poor-quality meat-armour on. Typically weak and slow undead deployed in large numbers for best effect. Modern virus variants aside, they usually just bite because it is about the only way they can inflict damage besides their terrible hygiene. There is no gain to them eating as they don't have functioning organs and are inherently disposable minions.
Ghouls on the other hand vary between the undead varieties and sometimes grotesque living humanoids, but their most notable feature is that they eat human flesh. Typically corpses in various states of decay, but often just as easily the living. They're almost always depicted doing so, and generally have insatiable appetites. But even the undead ones are considerably less decayed than zombies because the whole flesh-eating thing sustains them.
So, simply put, what the manga was describing as a ghoul was literally a zombie and what it described as a zombie was literally a ghoul.
Are the names given here exactly as written in the original or is it just translator interpretation of Japanese words?