The opener hit his second successive fifty while the allrounder followed his 67 with three wickets to crush Sri Lanka by 163 runs.
Tamim struck an unbeaten fifty to guide Bangladesh to an eight-wicket win over Zimbabwe
Bangladesh and Zimbabwe have a point to prove when they battle each other in a tri-nation one-day tournament in Dhaka from Monday.
After Bangladesh posted 190/4 thanks to half-centuries from Mohammad Naim and Saif Hassan the result was largely beyond doubt, hard though Namibia fought.
Bangladesh have made five changes to their squad which includes the inclusion of Mustafizur Rahman.
Aussies captain continued his reign in ICC Player Rankings for Test Batsmen while Indian skipper finish top in ODIs and T20Is.