Bangladesh, who had won the toss and elected to field, quickly had the hosts in trouble at 70-8 in the 20th over and it looked seemed as if the result was a forgone conclusion.
The lower-order resistance came when pace-bowling duo Nyamhuri and Ngarava, captaining Zimbabwe for the time in an ODI, added 63 for the ninth wicket that at least put some respectability to the total.
Nyamhuri scored 33 while Ngarava contributed 27 as Zimbabwe were eventually 141 all out in 36.4 overs, a total that still made Bangladesh heavy favourites to take a series lead.
The Tigers' bowling attack was excellent, led by 23-year-old paceman Nahid Rana who finished with career-best figures of 6-21 while fellow seamer Taskin Ahmed (2-32) chipped in with two scalps.
Bangladesh did not fare any better than their hosts with the bat as they slipped to 17-3 inside five overs with Blessing Muzarabani (2-24) and Ngarava (3-31) striking early in the wickets column.
Towhid Hridoy (25) and Nurul Hasan (31) led a brief recovery with a partnership of 49 but Nyamhuri (2-22) broke the stand when the left-arm seamer dismissed Hridoy in the 19th over.
Brad Evans (3-34) took the key scalp of Hasan and from their the procession of wickets continued as the tourists were bowled for a paltry 116 in the 34th over.
Sikandar Raza has returned to Zimbabwe's squad for the three-match ODI series at home against Bangladesh after missing the one-off Test match due to T20 commitments in England.
Innocent Kaia struck a maiden century before the bowlers starred as Zimbabwe recorded their biggest ever Test victory after thrashing Bangladesh by an innings and 85 runs in Harare.
The South African Women were made to work hard for runs as they eventually chased down 117 to defeat Bangladesh by four wickets in the Women's T20 World Cup at Lord's on Sunday.
Matt Renshaw struck a career-best 89 not out from 52 balls to help Australia beat Bangladesh by seven runs in the second T20I as the visitors took an unassailable 2-0 lead in the three-match series.
