The first decision is not which package to buy. It is how to divide limited days between wildlife, mountain and island experiences without turning the trip into a chain of transfers.
Start with the experience you would regret missing. Tanzania can combine wildlife safaris, Mount Kilimanjaro and Zanzibar, but doing all three well requires enough days and sensible transfers.
If wildlife is the priority
Protect enough nights for the safari route before adding the island. Serengeti, Ngorongoro and Tarangire serve different purposes; more stops are not automatically better.
If Kilimanjaro is the priority
Do not compress acclimatisation simply to fit more destinations. TANAPA presents both summit and non-summit mountain activities, so travellers who do not want a full climb still have Kilimanjaro options.
If Zanzibar is the priority
Choose island location and length around the experience you want—beach downtime, culture, marine activities or a mix—rather than treating Zanzibar as a single interchangeable resort zone.
A useful comparison rule
Compare the number of meaningful experience days with the number of transfer days. A shorter list of places often produces a stronger trip.