Travelers to Tanzania may obtain entry visas at select ports of entry. ... a valid drivers license and be able to present valid vehicle registration.
If you have an International Driving Permit or International Translation of Drivers License , it needs to be renewed every year and since in Tanzania. Short-term tourists do not need to obtain local Tanzanian insurance Automobiles are admitted into Tanzania for 14 days, with extensions of 14 days up to a total of three months.   Failure to depart within the specified period can result in confiscation of the automobile pending payment of duty. When a Tanzania registered vehicle is driven out of the country for three months or longer, export authorization must be obtained from the Bank of Tanzania.
Persons intending to remain in Tanzania for more than six months are required to obtain a Tanzanian driver’s license
Tanzanians drive on the left hand side of the road. It is recommended that you travel with an international driving license if you plan to drive in Tanzania.

TRAVEL FROM TANZANIA TO KENYA: Americans traveling to Kenya from Tanzania may obtain a visa in advance at the Kenya diplomatic mission, or upon arrival at a port of entry. The Kenyan High commission in Dar es Salaam generally issues visas in one day or less. Travelers wishing to return to Tanzania must have valid re-entry permits or multiple entry visas. Travelers by automobile from Tanzania into Kenya may apply at the Tanzania-Kenya border for permission to enter Kenya. Persons entering Kenya by road for a period of more than six nights must pay a road tax.

TRAVEL TO ZANZIBAR: Zanzibar, although an integral part of Tanzania, has its own laws and regulations. A dress code exists but is not implemented; however, visitors are advised to dress conservatively. A valid passport is required for travel to Zanzibar.