McCullum notched 131 to help the Black Caps post a challenging 303-8 on a flat Abu Dhabi Stadium pitch before Styris (3-23) triggered a middle-order collapse which saw Pakistan bowled out for 239, leaving the three-match series level at 1-1.

Pakistan won the first match by 138 runs on Tuesday. The final match will be played in Abu Dhabi on Monday.

Chasing a daunting target, Pakistan got off to a solid start of 77 with Khalid Latif (45) and Salman Butt (59) setting the tempo. Even after Latif fell leg-before to New Zealand skipper Daniel Vettori in the 17th over, Pakistan were well on course.

Butt and Younus (19) added another 47 for the second wicket before Styris struck three times in ten balls to turn the match in his team's favour.

Bowling for the first time in 13 months, Styris had Younus smartly caught at short mid-wicket by a diving Ross Taylor and then next ball induced Shahid Afridi (0) to play into the same fielder's hands.

In his next over, Styris had Kamran Akmal (four) caught at short cover before Butt was run out after being sent back by Mohammad Yousuf.

Vettori then trapped Yousuf (18) to push Pakistan to the brink of defeat. Although Shoaib Malik (26) and Abdul Razzaq (35) resisted, it was too little too late against a professional New Zealand.

Earlier, New Zealand had McCullum to thank for repairing the innings through a second wicket stand of 126 with Martin Guptill (62).

Stripped of the vice-captaincy to allow him to concentrate on batting last month, McCullum steadied the innings, driving and cutting with authority during his 129-ball knock. He hit 14 boundaries and three sixes.

Guptill hit five boundaries and two sixes during his 70-ball knock before holing out to paceman Razzaq. McCullum also added 44 for the fifth wicket with Vettori (30) before Razzaq returned for his second spell to have the New Zealand captain caught behind off a miscued hit.

McCullum reached the three-figure mark off 108 deliveries. He was finally dismissed in the 47th over, bowled off an inside edge by paceman Umar Gul.