The selectors went for Shadman Islam and Saif Hassan as the openers. I don't know why Tamim was not selected. There was only one warmup match and he didn't got much of an opportunity to bat. But I heard that he performed well during the Dhaka Premier Division Cricket League (for Prime Bank). Perhaps the board wanted to give opportunity for some youngsters and may have made the decision thinking that Zimbabwe is going to be a relatively weak opponent. BTW, when was the last test victory for Zimbabwe against a full member? That was in 2018?