Stops zombified piglins from spawning because of nether portals, which in vanilla isnt possible to stop. By default it stops them from spawning because of portals completely, but can be configured with gamerules.

/gamerule pigmenSpawnInPortals [default: true] - toggle pigmen spawning in portals

/gamerule pigmenSpawnDelay [default: 2000] - how often pigmen spawn from portals, lower values means they spawn quicker, overridden by pigmenSpawnInPortals

Works in singleplayer or on servers.