What can you do in Tanzania?

Just a couple of suggestions:
  1. You can go on a wildlife safari
  2. You can hike Mount Kilimanjaro/Mount Meru

You can also go on a Coffee/Banana plantation tour and a waterfall tour
Zanzibar is part of Tanzania, you take the ferry across the ocean about 2 hours and there are many things you can do on the island and on the coast!