If you do not comply with a New Zealand subpoena served in Australia, the court that issued the subpoena can give a certificate. This certificate says a Judge gave permission to serve the subpoena and you failed to comply with it. The court can do this on its own or if a party to the proceedings asks for it, and it must be in the prescribed form, which you can find out more about by looking at the relevant court rules or by checking the Trans-Tasman Proceedings Act 2010 for more information. You can also look at section 12 of the 1994 Act to compare. The court's decision is based on the fact that you did not follow the subpoena, and this can have serious consequences.