>>2058646All right sure, I'll fill you in. That specific zombie is supposed to be a trap to block you in the room after you pick up the progression key item in that room. You're supposed to blast its shit in with your shotgun or grenade launcher depending on the character you're playing.
And to follow up on what
>>2058574 said, the zombies in the game all have different health values and they're specifically designed to be annoying in certain cases. It's intended.