Zombified Piglins, Hoglins and Zoglins can all be killed by fire.
To reproduce:
Spawn or find one of the aforementioned mobs
Set them on fire with a Flint and Steel or fire aspect sword.
You should see it die.
Linked issues
Comments 2
Thank you for your report!
We're actually already tracking these issues at MCPE-65381, MCPE-66356, and MCPE-69178 so I will resolve and link this ticket as a duplicate.
If you would like to add a vote and any extra information to the main tickets it would be appreciated.
If you haven't already, you might like to make use of the search feature to see if the issue has already been mentioned.
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This is intentional