I have been tagged by few, so answering in general....
The fundamental difference between this T20 series and that CT win was that, this series was between top 2 sides in ranking table - could have gone either way. Ranking table is formed over the years' performance, hence it hardly lies - both PAK & NZ are quite good T20 sides. Had BD (Ranked 10) beaten NZ 2-1, we could have said that - but still it would have taken 2 flukes. Similarly, PAK's CT win took 4 flukes, if we say so ..... rather team playing exceptionally well in clutch games is better explanation. But, one thing we have to agree - that PAK side won't have drawn much money on a betting table, based on probability.
If I start to shoot an apple 100 metres away, may be 1 out of 500 times, I'll hit it - that 0.20% chance; but my first shot can also knock it - none will wait for me to miss the next 499, thereafter ...... Overall, PAK's ODI team isn't good, actually poor - that's evident in ranking table as well, based on years long results. 12 of that 15 CT winning squad were in NZ, very similar condition like UK, and got robbed. Also, we should understand that, ranking table actually favors PAK because among major teams, PCB is the only board that plays possible/available best XI even in a dead rubbers at home, against ZIM. Most teams actually do lots of permutation/combination for such bilaterals, which means they are not at 100 in such series, result of which forms the table.
I have my own explanation for that CT win (& our SF as well). Cricket despite being a team game, dominated by individuals. In a squad, IF few world class individuals can play their top game and others reach their career high, miracles can happen. I can give 3 examples to explain this - that Indian team of 1983 had Kapil, Sunny, Jimmy, Kirmani playing their A game, but players like Shandhu, Binny, Madan, Patil.... raised their game to career high level and that team beat WI twice in that tournament. 2nd one is SRL of 1996 - apart from Hari, Sanath, Arjuna and young Murali, Vaas, hardly any star name that people will remember for long. But, that team had everyone performing and those few top players led from front based on what Kalu, Guru, Mahanama, Tilakratne, Dharmasena, Wickramasinghe could contribute. 3rd is Bangladesh of 2015 - we covered 29 ranking points to qualify for CT 2017, in 10 months run, when Shakib, Tamim and Mushi were at their peak and players like Mahmudullah, Rubel, Nasir, Kayes punched well above weight, and we had couple of exciting youngsters debuting within that run - Mustafiz & Soumya.
For PAK, in 2017 CT, it was a similar case - Sarfraz led well, youngsters like Hasan, Fakhar, Shadab, Fahim played well above expectation; Amir, JK led the bowling charge... more importantly, there was not much baggage to carry - even Malik, MoHa, Azhar played well above expectation. If so many things click for a team, it can achieve lot more than expected.
For the last part, I can explain also why this nose dive in NZ (despite having 11-12 of CT winning players in it) and it'll be blood shed, if Ul Haq takes same squad to SAF or ENG - even AUS/NZ will decimate this squad in UAE. The reason being the curse of such raise - often teams fell in the trap of retaining winning squad. That PAK team had several over aged players who are well beyond their sell by date - hanging on the cliff on youngsters' shoulders. Every passing day, they are actually sinking deeper & deeper, which is pulling the team down. I always say - if seniors can't lead from the front in critical moments, they are actually counter productive, because experience makes them selfish & cunning - they know how to manipulate.
This NZ ODI tour was absolute shambolic, because of the poor squad selection and the gravity of the baggage. Ideally, PCB should have arranged an ODI farewell game for MoHa, Malik, Azhar, Wahab just after CT (I would have dropped Sarfraz as well from Captaincy, but carried him in squad with a back-up WK, to keep him honest) and use that SRL series to try at least 6 new/come back players, who are at the right age for 2019 and fits the bill of an ODI WC in UK. It might not have been 5-0 in UAE, but it would have been lot better in NZ for sure.