Deepak Chahar bowled an incisive opening spell before Shikhar Dhawan and Shubman Gill hit fifties to power India to a clinical 10-wicket win.
It was the record ninth-wicket stand of 70 runs between Brad Evans (33) and Richard Ngarava (32) that took Zimbabwe close to the 200-run mark.
In response, Dhawan and Gill put up a 192-run partnership to help India get past the finish line in just 30.5 overs. Dhawan scored 81 from 113 balls and Gill a more brutal 82 from 72 deliveries.
In bowling, it didn't take long for Chahar to find his rhythm on a Harare Sports Club track that offered some help. Chahar, who bowled unchanged for seven overs with first spell figures of 3/27, was well supported by Mohammed Siraj (1/36), who worked up a brisk pace while bowling the ideal Test match length.
Prasidh Krishna (3/50) and Axar Patel (3/24) also got their share of middle and lower-order victims.
Earlier, Rahul, who made a comeback after a nearly three-month layoff due to a sports hernia and Covid-19, won the toss and elected to bowl. Rahul took the captaincy reins in Rohit Sharma's absence, with India in good ODI form after winning five of their last six matches. Chahar also returned to the eleven after recovering from a hamstring injury that he sustained back in February this year.