Keep the safari coherent
Use a focused Tarangire–Serengeti–Ngorongoro route rather than squeezing in every northern park. A flight from the bush or Arusha can protect a meaningful first evening on the island.
Choose what Zanzibar means to you
Three nights is enough for a beach reset or a Stone Town and coast split, but not both at a slow pace. Decide whether culture, diving, swimming or rest is the priority.