''It will go down as a great test victory."
Williamson looked a touch shellshocked by what had unfolded, and the speed at which it happened.
That is the big part of collapses like this. It's as if a virus is running through a team.
Players aren't prepared to go out and can get psychologically caught short.
Equally bowlers get on a roll and Williamson had high praise for his five who kept the pressure on Pakistan, forced the run rate to edge up, making the challenge taller.
He confirmed the run out of wicketkeeper Sarfraz Ahmed, courtesy of slack running and Colin de Grandhomme's bullet throw from fine leg, was the key.
''He's a dangerous player. That was a big moment, but I guess when you take nine wickets in a session they're all pretty big moments.
''With the new ball around the corner, if we could open up an end, take a wicket and get a new batsman out to face the (second) new ball we would be in with a slim sniff."
There were 8.5 overs, or 53 balls, left when Neil Wagner completed the job. Not much breathing space, but enough.
Anatomy of Pakistan's second innings
59.6: Azhar Ali chops Mitch Santner onto his stumps. 131-1
67.4: Babar Azam is out to Santner in a ditto dismissal. 159-2
72.3: Sami Aslam slaps man of the match Tim Southee to deep mid off. 181-3
76.6: Sarfraz Ahmed run out with schoolboy running and fine throw from Colin de Grandhomme. 199-4.
81.1: Asad Shafiq gets a leading edge to Matt Henry, caught by Henry Nicholls at point. 204-5
84.3: Younis Khan shoulders arms at Southee. NZ referred the not out decision and got the DRS call. 218-6
89.5: Sohail Khan misjudges a push to cover off de Grandhomme to be caught at cover by Nicholls. 229-7
90.2: Mohammad Amir touches Wagner to wicketkeeper BJ Watling. 230-8
90.4: Wahab Riaz caught behind two balls later off Wagner. 230-9
92.1: Imran Khan splendidly caught at shot leg by Tom Latham. Game over. 230 all out.