Question: How come Alex's parents or any other character from the last movie don't make, at least, a small appearance in this movie? I know that Bernie Mac, who voiced Zuba, is dead, but can somebody explain Zuba and Florrie's fate?
Answer: They don't appear because Zuba's voice actor, Bernie Mac, passed away and their absence was done out of respect for him.
Answer: They don't make an appearance because they were irrelevant to the story. The decision to go back home would have been made with or without any character introduced in the previous movie, so they were simply not included. Alex's parents would have continued to live in Africa after Alex and the others left.
Casual Person
That makes no sense though because (I know it's a kids movie) but the way they portray it, it makes it seem like Alex doesn't care about leaving his parents and what he just recently realised is his birth home. Like, it feels like there was some necessary dialogue there (probably not for the kids though).