We do have some problems with trafficked sex workers, but the police investigate them as crimes. The other prostitutes can cooperate with the police without fear.
Practically nobody knows what Aotearoa is.
I'd like to see a private members bill for a referendum to get rid of the name New Zealand much like how Australia got rid of New Holland. Probably to coincide with the country leaving the commonwealth and becoming a republic and getting a new flag.
However, on topic, legalising prostitution means that prostitutes operate from licensed facilities that must confirm to workplace safety and health codes, it means the prostitutes and clients both have protection under consumer law as well as regular law and can go to the disputes tribunal or police if there are any issues.
You control underage prostitution and human trafficking because people who operate must be licensed and audited. Most consumers would go to licensed facilities because they operate completely in the open (even as crass as having big neon signs with SEX written on them), and are easy to find, street prostitution is illegal as are unlicensed brothels and both seem to have disapeared.