Watene-Zelezniak was born in Hamilton, New Zealand, and is of Māori, Tongan and Polish descent and is from the Waikato Tainui Iwi.

[6] On 26 June 2013, in the curtain raiser to Game 2 of the 2013 State of Origin series, Watene-Zelenziak played for New South Wales under 18’s against Queensland under 18’s at Suncorp Stadium, scoring a hattrick of tries in the 56-6 smashing win.

[12] While playing in the Panthers NSW Cup side, Watene-Zelezniak was hit with a 4-match suspension after he performed an eye gouge on a Wyong Roos player during their 32–24 win.

[16] On 28 April 2015, Watene-Zelezniak was ruled out of making his international debut for New Zealand in the 2015 Anzac Test after he was charged with a dangerous throw on Cronulla-Sutherland Sharks player Wade Graham.

[17] In Round 18, against the Sydney Roosters, Watene-Zelezniak suffered a collapsed lung during the Panthers 24–4 loss at Penrith Stadium and was ruled out for the rest of the season.

[23] On 6 May 2016, Watene-Zelezniak made his international debut for New Zealand against Australia in the 2016 Anzac Test, playing on the wing in the 16–0 loss at Hunter Stadium.

On 5 October 2017, Watene-Zelezniak was named in the 24-man New Zealand Kiwis squad for the 2017 Rugby League World Cup.

On 9 June 2019, Watene-Zelezniak was released from his contract with the Penrith Panthers effective immediately to sign with the Canterbury-Bankstown Bulldogs.

During the mid-way part of the season, Canterbury found themselves sitting last on the table and in real danger of finishing with the wooden spoon.

However, for the third straight season, Canterbury achieved four upset victories in a row over Penrith, the Wests Tigers, South Sydney and Parramatta who were all competing for a place in the finals series and were higher on the table.

[38] On 2 July, Watene-Zelezniak played his first game for the New Zealand Warriors in a one point loss to St. George Illawarra.

[40] In the second group stage match at the 2021 Rugby League World Cup, Watene-Zelezniak scored four tries in New Zealand's 68-6 victory over Jamaica.

[46] He played 24 games for the New Zealand Warriors in the 2023 NRL season and scored 27 tries as the club finished 4th on the table and qualified for the finals.

[49] On 12 February, it was announced that Watene-Zelezniak would be ruled out indefinitely after dislocating his wrist during the New Zealand Warriors trial game against Cronulla.