New Zealand were scuttled for 99 as Gul produced a superb spell of fast bowling to take 5-6, while Abdul Razzaq vindicated the decision to recall him to the side in place of Sohail Tanveer by taking 2-17.
"It was a fantastic spell," Pakistan captain Younis Khan said of Gul's bowling. "If we can have a spell like that in every game we can beat every team in the world."
Gul managed to reverse swing the ball, confounding New Zealand's batsman.
"It is not the first time he has done this," Khan said. "He has a good action to reverse swing the ball, he has pace and he played here for Surrey (last season) so he knows this ground."
Kiwi captain Daniel Vettori said he'd never seen anything like it.
"He started to reverse swing it after 12 overs and I don't think that's ever happened in the history of Twenty20 cricket," he said. "It made a massive difference. I don't know how he did it."
Scott Styris was New Zealand's top scorer with just 22.
Pakistan coasted home to finish on 100-4 with Shahzaib Hasan making 35 and Shahid Afridi 29 not out.
Daniel Vettori, back in the side after recovering from a shoulder injury that kept him out of the first three games, won the toss and decided to bat first.
His vice-captain Brendon McCullum smacked a quick 12, but was caught by Fawad Alam off the fourth ball of the second over, bowled by Abdul Razzaq.
Aaron Redmond made just 5 before he was caught by Gul off Mohammad Aamer in the fourth over, and Razzaq trapped Martin Guptill lbw in the fifth.
Shahid Afridi got rid of Jacob Oram, who miscued to Misbah-ul-Haq, and Afridi then produced a brilliant running catch to dismiss Styris, who had tried to hit Gul out of the ground.
Peter McGlashan was given out lbw, attempting to sweep Gul, leaving New Zealand in deep trouble on 73-6 in the 13th over.
Gul then ripped out Nathan McCullum's leg stump in the 15th.
In his final over, the 17th, he bowled James Franklin's middle stump, then had Kyle Mills caught by Shahzaib Hasan with his next ball to set a new record in Twenty20 internationals.
New Zealand failed to complete its 20 overs when Vettori was run out with eight balls to spare.
Pakistan's chase wasn't entirely free of risks, but they raced to 36 from four overs before Kamran Akmal was caught by Guptill off Mills.
There was a mild stutter when Vettori had Razzaq caught behind for 5 and Hasan was run out in the seventh over.
Vettori then had Shoaib Malik caught by Nathan McCullum in the ninth over but Afridi and Pakistan captain Younis Khan eased to the target with five overs to spare - Afridi hitting the winning runs as two New Zealand fielders collided with each other.
"It was a very good wicket and there were plenty of runs on it," Vettori said. "But we didn't put a score on the board which meant we were under constant pressure. We needed around 180 to compete and it didn't happen today."
