Wah! Sounds fun!
10 hours with a toddler. Hmm. It can be done pretty smoothly if you are well prepared. Easy activities that will distract lo, these are moments I would also be lax about screen time and snacks!
+ choose seats that give you the most space to move around. Some parents book an extra seat. Some parents choose 1 business class seat, 1 economy and split themselves up so that there will be 1 awake parent and 1 fully rested one.
+ Take turns carrying if need be, sometimes, they just need to be comforted as plane ride is a restless activity even for adults.
+ Get lo used to long rides, start with a weekend trip M'sia by train?
+ Be nice to other people but ignore them if they give loud sighs or roll their eyes down the aisle. They. Don't. Know.
Here are more tips on https://sg.theasianparent.com/travelling-by-plane-with-your-child/
Enjoy NZ!