Lomax moved back to New Zealand after spending time there during his childhood and joined Bunnings NPC side Tasman during the 2017 Mitre 10 Cup, making his debut against Otago at Forsyth Barr Stadium.

The Highlanders announced the signing of the former Melbourne Rebels player in September 2017 committing his future to New Zealand rugby.

Lomax became All Black number 1180 making his debut against Japan in Tokyo in November 2018, but did not play for the side again until 2020 where he made 5 appearances.

Lomax was picked for the 2023 Rugby World Cup and started in the Final, an 11–12 loss to South Africa.

In 2024, Lomax was named the Tom French Memorial Māori Player of the Year at the annual New Zealand rugby awards.