"cz" marks the same sound as the English "ch". "j" marks the same as "y" in "yes". Otherwise you read it letter by letter, a bit as if it was Spanish.
So... Is Ch'yvinos'tavch legible enough? :) Although, the pronounciation of the j would be so weak that you could perhaps skip it. It does alter the sound a bit, but doesn't really sound as an independent sound in this word. So, also Ch'vinos'tavch could maybe be a valid transcription? And of course real Polish language does not have the combination czj anyway :)
They are the locals. They are indigenous New Zealanders and they are doing something that is customary in their culture in the kind of situation they were in during that session.
The New Zealand lawmakers were trying to pass a bill that would have severely reduced the rights of the locals, and this reaction is part of how the local culture demands people to act.