For New Zealand, the main concern is their bowling. Gone are the times when Neil Wagner would rip through the opposition batting lineup, with support from Trent Boult and Kyle Jamieson. Wagner retired from international cricket early this year, and Boult has been focusing on franchise T20 stuff. Jamieson lost his way some time back and I don't think he will be back to national duty anytime soon. Now compared to this, batting looks stronger at least on paper. They have quality batsmen such as Kane Williamson, Devon Conway, Rachin Ravindra and Tom Latham in their squad.
We have this problem consistently for New Zealand as they are losing their pacers due to serious injuries while they are having their good time currently their attack is surely not quality as we have result of two test matches in this series, but luckily they are having good results in India thanks to their spinners which are doing good job, but sadly they are not effective at home like they have done job in subcontinent.
New Zealand is always having lacking quality players in cricket due to having good popularity in Rugby and Soccer which are currently having much better system they needed to work on like we have in Australia things can take good changes, and they can also achieve more success while their domestic system is also not bad.