The Cranberries had already had hits built on restraint and whispered vocals. Zombie threw all of that out. Written after a bombing in Warrington that killed two children, it is the sound of a singer who has stopped being polite.
The arrangement is deliberately simple, four chords and a drum pattern that never lets up, so there is nothing to hide behind. What carries it is the voice, moving from a low mutter to that drawn out cry in the chorus.
It remains one of the most streamed rock songs of the nineties, which says something uncomfortable about how relevant the subject stayed.