This is rather a suggestion than a bug, but when two hoglins, immune to zombification, breed in the overworld, their offspring is not immune to zombification. I think it would only make sense if the offspring was immune to zombification like its parents.
MC-213065
Issue with hoglins in the overworld
Resolved
Invalid
0
This report is invalid, as this appears to be a Feature Request. Please do not post suggestions on the bug tracker as this place is specifically used for tracking and handling bugs only. If you wish to share your ideas, you can do so on some of the following links.
Official Minecraft Feedback Page - https://feedback.minecraft.net/hc/en-us
Minecraft Suggestions Reddit - https://www.reddit.com/r/minecraftsuggestions