I visited the San Diego Safari Park in October 2021, and keepers there said that they have no plans to bring in a new bull. Maybe Zuli will become the breeding bull at SDZSP when he gets older.
Man, I really doubt the Safari Park have no intentions to import a bull. Zuli is related to all of the younger cows, and if a new bull isn't imported breeding cannot happen... may I ask where you got this info from?