If a pedestrian is jaywalking and crossing the road against the red light, should you slow down and let them pass?

Yes, you should yield.

New Zealand traffic regulations require all drivers to remain vigilant towards pedestrians at all times and take necessary measures to avoid accidents. Even if a pedestrian crosses the road without a crosswalk, runs a red light, or engages in other illegal behavior, drivers are still responsible for taking all possible measures to ensure the safety of pedestrians. Choosing to slow down and yield is a fundamental consideration for personal safety. Despite any unlawful or improper actions by pedestrians, drivers must do their utmost to avoid causing harm.