The Australian skipper belted 172 in the tri-series match to pass his previous mark of 156, which he set against England in 2013.
Finch continued his rich vein of form as he combined with opening partner D’Arcy Short to put on a 223-run stand – the highest partnership in T20I history.
His innings at Harare Sports Club came from only 76 balls and included 10 sixes and 16 fours.
Behind Finch’s two top scores, fellow Victorian Glenn Maxwell is next on the all-time T20I record list after he belted an unbeaten 145 against Sri Lanka in 2016.
Short was out for 46 with four balls left in the innings, while Finch was dismissed two balls later in a rare case of hitting his own wicket.
Australia finished their 20 overs on 2-229, setting Zimbabwe a target they were never going to chase down.
The hosts saw out their innings at 9-129 as Andrew Tye picked up three wickets.
It was Australia’s first win against Zimbabwe in T20s after being upset in their only previous meeting at the 2007 World Cup.
Finch finished only three runs behind West Indian Chris Gayle’s highest Twenty20 score of 175, which he hit in the 2013 Indian Premier League.
The 31-year-old said he was aware of all the records on offer while out in the middle, including Gayle’s mark.
He was captain of the Pune Warriors on the night when Gayle went ballistic for the opposing Royal Challengers Bangalore.
“He’s (Gayle) a great player and he deserves it (the record),” Finch said.
“(Today) was just one of those days where a few things went my way and I hit a few in the middle, which was nice.”
Finch’s T20I career average sits at 47.81, only behind Pakistan’s Babar Azam (53.00) and Indian captain Virat Kohli (48.58).
Australia carried on from where they left off against Pakistan on Monday after opening their campaign with a nine-wicket victory.
Finch’s team has secured their place in Sunday’s final ahead of their final two games tomorrow and Friday.
It comes after being on the other end of a one-day series whitewash in England. (Courtesy TV New Zealand)