Dane Cleaver scored an unbeaten 78 as New Zealand made 179 for four and Michael Bracewell took a hat-trick as Ireland were dismissed for 91 in the 14th over.
New Zealand lead the three-match series 2-0.
The tourists were asked to bat first again with Martin Guptill and Finn Allen putting on 44 for the first wicket, which then brought Cleaver to the wicket.
Playing just his second international, Cleaver hit his unbeaten 78 off 55 balls, which included five fours and four sixes.
Allen finished with 35 and Glenn Phillips 23.
Ireland started their run chase well with Paul Stirling hitting four boundaries in the 15 balls he faced before the wickets started to fall.
Ish Sodhi picked up three wickets for 21 runs, while Bracewell finished things off with three wickets off the last three balls of the innings.
His figures were 3 for 5 off 0.5 overs.
Captain Mitchell Santner couldn’t help but be impressed by what Bracewell achieved.
“There’s not a lot that (Bracewell) can’t do at the moment so I thought I’d get him in there. We’re pretty happy with the win today.”
Cleaver was named player of the game.
“The wicket offered a little bit of variation so it probably wasn’t my most fluent innings but you try to stick to your options so it paid off. Very special to have my family here.”
The final game is on Saturday morning.
A stuttering batting display has contributed to the Black Caps five-wicket loss to the West Indies in the first ODI in Barbados.
Chasing just 191 to win on Thursday (NZ time), the home side cantered to victory with 11 overs to spare.