I was playing on peaceful mode, there was a storm and first 1 zombie horse appeared, and after a few minutes about 50 of them appeared, when it became day and there was sun they died from it
Linked issues
is duplicated by 10
MC-308034
Zombie horses now spawn naturally on Peaceful, unlike Bedrock, and unlike other undead mounts
Resolved
MC-308464
Zombie Horses Spawning in Peaceful
Resolved
MC-308561
Zombie Horses spawn in flat world on Peaceful mode
Resolved
MC-308607
Zombie horses spawn in thunder
Resolved
MC-308721
Zombie horses appear every night
Resolved
5 more links
Big issue, 26.2 Snapshot 4 unintentionally caused this, as it's not stated in the changelog