He and Mitchell combined for 82 in 8.5 overs to lift New Zealand far from trouble at 65-3.
Their stand ended when Mitchell was bounced and caught by medium-pacer Josh Little for 48 off 32.
But new batter Jimmy Neesham then rushed the visitors to victory with 23 off six balls, including a match-winning six over midwicket.
Ireland was unchanged from the side which lost by 88 runs on Thursday and Paul Stirling gave them a great start with 40 off 29 and sixes off Jacob Duffy, Mitchell Santner and Ish Sodhi.
But Stirling's exit started a collapse, as Ireland went from 79-1 in the 10th over to 116-6 in the 17th. Sodhi slowed them down with 2-24.
Then Curtis Campher took 19 off bowler Blair Tickner, Mark Adair took 18 off Neesham, and the last over bowled by Duffy went for 13.
Adair had 37 runs off 15 and Campher 19 off eight and Ireland asked the question of New Zealand.
But the Black Caps, as usual, had an answer. They go to Scotland for three matches from Thursday.