After winning the toss and opting to bat, Kayla Reyneke top-scored with an unbeaten 34 while further contributions from Anneke Bosch (33), Miane Smit (30) and Faye Tunnicliffe (25) as the visitors got to a total of 164-6.
Smit and Tunnicliffe put on a 37-run partnership for the opening stand but the visitors then slipped to 79-4 inside 11 overs as Zimbabwe kept chipping away in the wickets column.
Reyneke and Bosch then came together and stitched together an important 75-run partnership for the fifth wicket hat came off just 54 deliveries.
Zimbabwe seamer Michelle Mavunga was the pick of the home team's bowlers with figures of 3-46 in four overs.
The hosts then were 22-2 in the fourth over as Proteas seamer Nthabiseng Nini striking a double blow, but Kelis Ndhlovu and Chipo Mugeri-Tiripano added 80 for the third wicket to give Zimbabwe hope.
Caitlin Wyngaard broke the partnership and the home team then slipped up in pursuit of the target as they eventually reached 150-8 in their 20 overs.
Nini finished with figures of 3-19 while Ayanda Hlubi also took three scalps while going for 24 runs in her four overs.
Travis Head struck a century as Australia beat Zimbabwe by 84 runs in the second ODI in Harare on Friday, with the visitors taking an unassailable 2-0 lead in the series with a game to spare.
South Africa Women produced a dominant display against Zimbabwe Women, securing an 80-run victory in the fourth match of their tour of Zimbabwe.
Matt Renshaw and Nathan Ellis starred as Australia opened their three-match ODI series against Zimbabwe with a 59-run victory in Harare.
Laura Wolvaardt struck a career-best 126 not out as the Proteas Women beat Zimbabwe by 80 runs in the third T20I in Bulawayo as the visitors wrapped up the series with two matches to spare.
