Chasing 136 for victory, the New Zealand opening pair hammered 66 runs in 29 balls, and hit 10 sixes between them to break the back of the tourists, already weakened by leaving the likes of Babar Azam and Mohammad Rizwan at home.
Allen struck a 16-ball 38 runs, with 30 of those coming via clearing the fence, while Seifert backed up his 44 from the series opener with a 45 off 22, and five sixes of his own.
By the time both batters were dismissed just shy of the seven over mark, New Zealand needed 49 runs from 49 balls, and coasted to victory with 11 balls to spare.
After a rain delay of more than an hour reduced the contest to 15 overs each, captain Michael Bracewell had no hesitation in bowling first, and was rewarded with regular strikes from his attack.
However, despite no batter managing more than the 28-ball 46 from captain Salman Agha, Pakistan were still able to score at exactly nine runs per over, to give the Black Caps a tricky chase of 136 from 90 balls.
New Zealand’s bowlers shared the wickets evenly, as Ish Sodhi (2/17), Jacob Duffy (2/20), and the returning pair of Ben Sears (2/23) and Jimmy Neesham (2/26) all took two apiece.
Quickfire cameos from Shadab Khan (26 off 14) and Shaheen Shah Afridi (22 not out off 14) at the very least lifted Pakistan past the 91 they scored in Hamilton.
In response, Afridi rattled the ribcage of Tim Seifert in the first over of the second innings. But even as Seifert played out a maiden first up, his opening partner cleared the ropes three times in the next over.
Given the short boundaries, seven of New Zealand’s eight first scoring shots were all sixes, as Seifert and Allen made the most of the powerplay. From 0/0 at the end of the first over, the Black Caps were 44/0 after three, as Allen and Seifert raised their half-century stand in just 24 balls.
Seifert in particular was so brutal, seamer Mohammad Ali was no-balled for sending down a delivery off the pitch, and saw the ensuing free hit belted over cover for four.
Tim Seifert against Pakistan in Dunedin. Photo / Photosport
One ball later, though, Seifert holed out to Afridi at mid-on, and departed for 45 runs from 22 balls, with 42 of those runs coming via three fours and five sixes.
Having started the innings needing 136 from 90 balls, that equation was just 70 off 60 by the time the powerplay ended at 66/1.
Undeterred by the loss of his partner, Allen welcomed Jahandad Khan to the bowling crease with a four over cover, and sixes over long-on and midwicket, to bring the required run-rate to less than a run a ball.
Jahandad had the last laugh, though, as he trapped Allen LBW for 38 from just 16 balls. But the damage was ultimately done.
A mini-collapse of three wickets in 12 balls gave Pakistan hope of snatching victory, as Mark Chapman and Jimmy Neesham departed quickly, but it was too little, too late.
A 35-run stand between Daryl Mitchell (14) and Mitch Hay (21 not out) got New Zealand close to the target, before captain Bracewell sealed the victory with a pull over midwicket to complete the chase with time to spare.
New Zealand 137/5 (Seifert 45, Allen 38; Haris Rauf 2/20)
Alex Powell is an online sports editor for the NZ Herald. He has been a sports journalist since 2016, and previously worked for both Newshub and 1News.
