Quinton de Kock smashed his fourth century of the World Cup and Rassie van der Dussen also hit a ton as South Africa sealed a comprehensive 190-run victory over New Zealand on Wednesday.
It's the semi-finals-bound South Africa's sixth win in seven matches.
New Zealand were left needing a rescue act after collapsing to 90-5 inside 19 overs while chasing 358, with only Will Young (33) and Daryl Mitchell (24) offering any resistance, but the Proteas did not relent and dismissed them for 167 in 35.3 overs.
Pace bowler Marco Jansen (3-31) began the rout with an early double strike, while spinner Keshav Maharaj (4-46) landed timely blows to ensure New Zealand had no way back at the MCA Stadium in Pune despite a defiant 60 by Glenn Phillips.
In a highly-anticipated contest days after the two nations clashed in the Rugby World Cup final, De Kock struck 114 and Van der Dussen exploded late on to score 133 for his second century of the showpiece as South Africa posted 357-4.
"Clinical display I would say," South Africa captain Temba Bavuma said. "With the bat we handled the challenge up front and with the ball nipping around. The big partnership really set it up for the boys.
"With the ball, we sustained the pressure throughout their innings... Quite clinical with the execution of our skills."
Victory helped South Africa leapfrog India to the top of the standings while New Zealand are still in the hunt for a place in the semi-finals in fourth.
The Proteas built on the De Kock and Van der Dussen's 200-run stand with 119 in the last 10 overs as David Miller put the New Zealand bowlers to the sword with a 30-ball 53.
South Africa began steadily after New Zealand skipper Tom Latham won the toss and opted to bowl, as they shrugged off the dismissal of Bavuma (24) and flexed their muscles with top-scorer De Kock going past 500 runs in the tournament.
De Kock, who will retire from the 50-overs format after the tournament, milked the Black Caps bowlers in a flawless innings and reached his century with a massive six over long-leg off Jimmy Neesham before looking to accelerate.
He scored two more boundaries but offered a simple catch to Phillips at backward point as Tim Southee (2-77) took his first wicket on his return to competitive action after right thumb surgery in September.
Southee castled Van der Dussen on a day of little joy for New Zealand, who had lost the bowling services of seamer Matt Henry due to a right hamstring problem midway through South Africa's innings.
Neesham was struck on the hand while stopping a ball off his own bowling and was only able to bat at number nine, although he did not suffer broken bones.
"Not our best performance," said Latham, whose side face Pakistan next. "We were put under pressure with that massive partnership Rassie and Quinton had up top.
"At the halfway mark it was a big score but a decent surface. From a batting point of view you need partnerships. To be three, four, five down early and with our backs against the wall, we weren't able to build those partnerships.
"Disappointing the way it panned out."