After being sent in to bat, South Africa posted an above-par 187 for four in their 20 overs, before they restricted New Zealand to 154 for eight in reply.
Both teams were fielding depleted squads and giving fringe players a run, and from a South African perspective it was certainly Esterhuizen who has impressed the most in the series.
He was again the pick of the South African batters as he smashed 75 from 33 balls in which he hit six sixes.
He is easily the leading scorer in the series for both sides with exactly 200 runs at an average of 50.00 and a strike rate of 145.98.
“The nice thing was I got to play with freedom and express myself,” Esterhuizen said. “In my mind, the openers assessed and said 160 would be competitive and me and (Dian) Forrester thought 180 would be a good score and we ended up with 187.
“I think from the first match (in the series), there was a bit of a graft and you have to play some dots. Then it was a bit more free-flowing and you could get into strong positions and that sets you in good stead.
“It means everything to me and is a ‘pinch-me’ moment to play for your country. It’s a special feeling and humbling.”
He found support from Rubin Hermann, who supplied a breezy 39 from 31 deliveries, while Wiaan Mulder scored 31 from 29 deliveries at the top of the order.
Seamer Ben Sears was again impressive for New Zealand with 2-37 in four overs.
South African-born Bevon Jacobs smashed 36 in 19 balls for New Zealand in reply, but no-one else really managed to get going.
Seamer Gerald Coetzee was superb with his variations and took 2-21 in his four overs.
Spinner Prenelan Subrayen also bowled with excellent control as he recorded figures of 0-22 in four overs, piling the scoreboard pressure on the home side. Seamer Ottneil Bartmaan took 2-33 in four.
"It's a wonderful opportunity for these youngsters to understand international cricket," South Africa captain Keshav Maharaj said.
"We saw the hunger and desire and it shows the depth in our system. From 2-1 down, to see the youngsters come through for two good performances with the bat, we can be really happy."