Leg-spinner Vandersay broke through Zimbabwe's middle-order resistance before seamer Gunaratne made short work of the tail, as the hosts were rolled for just 160 after winning the toss and electing to bat first.
After sneaking into the final via a tight win over the West Indies in Friday's rain-affected game, Zimbabwe shuffled their line-up for the final but could not solve their top-order woes.
Openers Brian Chari and Chamu Chibhabha were both left out, with Peter Moor promoted to the top of the innings and Tarisai Musakanda given an nternational debut at No. 3.
Although Musakanda and Craig Ervine revived the innings after the rain delay with a 53-run stand for the third wicket, Vandersay intervened when he had Ervine caught and bowled for 25, then had the debutant caught at slip for 36.
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With Sachith Pathirana dismissing Sikandar Raza Butt and Malcolm Waller in the space of three overs, and Vandersay taking care of captain Graeme Cremer, Zimbabwe slid further to 133 for seven.
The all-rounder finished with figures of 3 for 10 from 4.3 overs, while Vandersay took 3 for 50 from his 10 overs.