South Africa won the toss and sent India into bat, restricting the visitors to 211 all out in 46.2 overs on a wicket that was not easy to score on.
They chased down their target with 45 deliveries remaining to set up a series decider in Paarl on Thursday.
De Zorzi playing in his fourth ODI and a replacement for Quinton de Kock at the top of the order, started cautiously before taking the attack to the tourists as he put on 130 for the first wicket with Reeza Hendricks, who scored a more sedate 52 from 81 balls.
The rate accelerated in a second wicket stand of 76 with Rassie van der Dussen (36) as India’s bowling attack failed to apply the same pressure with the ball as their hosts.
"It was a flood of emotions," De Zorzi said of his maiden ODI century.
"I first thought of my Mom, hopefully, she was back from work and watching.
"There have been a lot of doubters (of his ability) and you are just happy you could prove it to yourself and to the people who care about you. I will never forget this moment."
India had skittled South Africa for 116 in the first game of the series in Johannesburg on Sunday, the latter’s lowest-ever score on home soil, as the visitors won comfortably by eight wickets.
They looked set for a competitive total in Gqeberha when they reached 114 for two but lost their last eight wickets for the addition of 97 runs as South Africa put the squeeze on the scoring rate.
Seamer Nandre Burger took 3-30 in 10 overs, with Beuran Hendricks (2-34), in the side for the injured all-rounder Andile Phehlukwayo, also among the wickets in his first ODI since April 2021.
India opening batter Sai Sudharsan followed up his unbeaten half-century on debut with a fluent 62 from 83 balls, while captain KL Rahul scored 56 from 64 balls. They were the only two innings of any substance.
"We thought even 240-250 would have been a good score," India captain Rahul said. "With a set batter, we might have got those runs. We lost wickets at crucial times."
Both sides have rested key players with a two-match Test series to follow, starting in Pretoria on December 26th.
