Marzhew has scored 59 tries in 86 games for Newcastle, where he and Dom Young rank among the NRL's most effective wingers.
At 29, he is preparing for a semi-final in New Zealand as a key attacking outlet and powerful runner.
His move followed Sam Verrills' collarbone injury late in 2022, prompting Gold Coast to request Newcastle hooker Chris Randall in the exchange.
Marzhew had spent three seasons with the Titans and made his NRL debut under Justin Holbrook in 2021.
He competed with Corey Thompson, Anthony Don and Phil Sami, whom he called "the safer options".
"It all happened so quick ... it shocked me that week. Because I'm finding out, and then two days later, I'm driving up here," Marzhew said.
Holbrook's arrival has helped Newcastle score 12 more points per game than in 2025.
Marzhew said, "I was a fringe player at the time," but added, "He gave me my NRL debut."