It was Kelis Ndhlovu who finally put an end to the opening partnership when she had Lewis caught out for a brilliant 47-ball 69.
Nkomo sent back Hunter for 71 in the 17th over, but by then Ireland had already crossed the 150-run mark.
They finished on 176/3 in their 20 overs to set a formidable target for Zimbabwe.
In response, Ava Canning struck twice in the Powerplay, sending back Sharne Mayers and Chipo Mugeri-Tiripano cheaply to give Ireland an even stronger grip on the game.
Skipper Mary-Anne Musonda and Modester Mupachikwa combined to lift Zimbabwe out of trouble and at the end of 10 overs, the team moved to 65/2, still quite some distance away from the big target.
Laura Delany broke the stand with the wicket of Mupachikwa, cleaning up the wicketkeeper for 27, but Musonda carried on for a bit more to finish on 48.
Zimbabwe, however, went on to lose their next four wickets in the space of 22 balls and eventually finished on 120/8. They have one win in three games and will need a big one in their final game to stand a chance of making it to the semi-finals.
Meanwhile, with two wins in two games, Ireland are at the top of Group B and are favourites to make the semis now.