Captain Azhar on 36 and Aslam on 32 have seen off the new ball but their caution has lifted the required run rate from 3.65 to 4.73 and the Test appeared destined for a limited-overs-style finish.
Pakistan need victory to retain their number two Test team ranking as either a draw or a defeat could push them down to fourth behind India, England and Australia.
New Zealand, needing a win to take the series 2-0 and boost their ranking to six, turned to spin for the last half-hour of the morning session after their seamers could not find a way through despite heavy cloud cover.
After 20 overs, Pakistan were on 21 with Azhar 11 and Aslam 8. By 30 overs the pace had quicked to 55 with Azhar on 29 and Aslam 18, and the last nine overs before lunch added 21.
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Aslam was gifted a life just before the adjournment when an lbw appeal from Colin de Grandhomme was turned down.
Kane Williamson, having wasted one-referral, debated too long on whether to appeal again and his chance to request a review timed out.
New Zealand wasted the first of their two reviews when Azhar, on 17, was subjected to a half-hearted appeal for caught behind off Matt Henry which was turned down.
With New Zealand desperate for a breakthrough, Williamson referred the decision to the TV umpire and replays to show the ball flew harmlessly past Azhar at chest level.
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