Not much of a solution but things about zombies you have to kill
a CEDA agent is immune to fire and might drop a boomer bile.
a clown attract hordes.
mudmen will crawl using their hands and feet and may be hard to see when they're in the water. If you kill them while they're in the water a bunch of times, you'll get the DEAD IN THE WATER achievement. If they hit you after or while in the water, your character will be partially blinded.
construction workers have earmuffs so they cannot hear pipe bombs and will not be attracted to boomer bile.
Some campaign dlcs like Cold steam have some of these.
The Riot zombie was removed in some countries
The fallen survivor does not count to this achievement.