After New Zealand had made a competitive 185 for seven having being sent in to bat in damp conditions, McCullum raced through the Pakistan middle order to finish with four for 16 from four overs.
Pakistan were left 146 for nine after its 20 overs, conceding the series ahead of the final match on Thursday.
Score Board
New Zealand
Ryder c Akmal b Razzaq 0
Guptill c Afridi b Ajmal 44
Franklin c Akmal b Afridi 40
Taylor (not out) 30
Styris c Shehzad b Akhtar 34
McGlashan lbw b Riaz 26
McCullum c Shafiq b Ajmal 1
Mills st Akmal b Ajmal 0
Extras (B-1, LB-4, W-4, NB-1) 10
Total (for 7 wkts, 20 overs) 185
Fall of wickets: 1-0, 2-91, 3-94, 4-133, 5-175, 6-184, 7-185.
Bowling: Razzaq 2-0-12-1, Akhtar 4-0-42-1, Gul 3-0-47-0, Riaz 3-0-22-1, Afridi 4-0-22-1, Ajmal 4-0-35-3.
Pakistan
Hafeez (run out) 46
Afridi b Mills 7
Shehzad c Styris b Butler 15
Akmal c McCullum b Southee 26
Khan c McGlashan b McCullum 3
Shafiq b McCullum 6
Razzaq c McGlashan b McCullum 14
Gul c Guptill b McCullum 0
Riaz c McCullum b Southee 18
Akhtar (not out) 5
Ajmal (not out) 0
Extras (LB-5, W-1) 6
Total (for 9 wkts, 20 overs) 146
Fall of wickets: 1-24, 2-68, 3-69, 4-76, 5-96, 6-114, 7-114, 8-141, 9-141.
Bowling: Franklin 1-0-10-0, Mills 3-0-34-1, Southee 4-0-26-2, Butler 4-0-35-1, Woodcock 4-0-20-0, McCullum 4-0-16-4.
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