A paediatrician has said if Trish hadn't adopted him and brought him to New Zealand he would not have survived.
He is now an active 8-year-old who attends Dannevirke's Totara College.
Trish works part-time in Dannevirke as a care assistant in a retirement home.
She is a single parent, finishing work mid-afternoon so she is home when Zac arrives from school.
In 2015 she led a huge local effort to support Zac's home village when it was devastated by Cyclone Pam.
Trish organised container-loads of donated essential supplies from our community to help villagers get back on their feet.
But now, she needs help herself.
"Zac wants to go to Vanuatu with his school at the end of the year and this visit is more urgent now as I'm not well," she told the Dannevirke News.
"I didn't think it would be possible for the two of us to afford the trip, but Mike Stone, who has had a lot to do with Zac as his RTLB [Resource Teacher Learning and Behaviour] teacher, convinced me."
Trish's medical condition is worsening rapidly and she will eventually be fed through tubes in her stomach.
"They were going to operate, but there's a huge risk," she said.
"When I eat, the doctors don't know where the food goes. Soon I won't be able to eat or drink again, it'll just be the tubes.
"I've told Zac about my health, but I know how much he wants to go back to Vanuatu to see his family."
The last time Zac visited Vanuatu he was 3 and very sick. He doesn't remember the visit.
"He's such a treasure and I want to do this for him," Trish said.
Mr Stone worked with Zac for a short time early last year and has supported this effort to visit Vanuatu.
"Long-term outcomes are better for young people who have an awareness of their own cultural identity, strong family connections and an understanding of their own heritage," Mr Stone said.
"A trip to Vanuatu would give Zac all of the above."
Trish's medical condition will mean she will not be able to travel to Vanuatu from next year because she will need comprehensive medical support, but with Totara College students visiting the island this year, she hopes to accompany Zac and visit his home village.
• You can help Trish raise the money she needs by going to https://givealittle.co.nz/cause/zactovanuatu