And only for party members; there are no restriction on the general public saying who they voted for.

No one is allowed to campaign for anyone. There are no exceptions for non-party members.

This is what I can find: https://elections.nz/guidance-and-rules/advertising-and-campaigning/social-media

Using social media on election day

On election day additional restrictions apply when you’re posting on social media.

From midnight before election day until 7pm on election day, you can’t post or share any content that’s likely to - or is intended to - influence someone’s candidate vote or party vote.

Paid online election advertising is prohibited on election day.

The election day rules make no exemption for the expression of personal political views online.

In another section:

On election day you can remind people to get out and vote, and even tell them that you’ve just voted – but you should take care not to post anything that encourages other voters to vote (or not to vote) for a particular candidate or party.