After being signed by the former Brisbane Roar coach Frank Farina on a two-year contract, Zullo played five of the six opening games of the season, coming on as a substitute. On his first eleven debut against Wellington Phoenix, his sixth appearance for Queensland, he scored in the opening minutes of the game and set up a first half added-time goal for fellow youngster and close friendRobbie Kruse. He previously played in the Brisbane Premier League for the Brisbane Strikers During a match against Sydney FC, Zullo limped off the field with a torn thighmuscle which ruled him out for 6 weeks. At the end of the 2008–09 season, Zullo received offers from Dutch Eredivisie clubs FC Groningen and NEC Nijmegen but declined both offers and cited his preference to stay in the A-League for another season. On 2 April 2010, along with fellow Roar players, Thomas Oar and Adam Sarota, Zullo joined Dutch side Utrecht on a three-year deal, in a collective transfer deal rumoured to be worth in excess of A$1.8 million. He made his debut for Utrecht in a 1–1 draw with NEC Nijmegen on 28 February 2011, coming off the bench on the 81st minute. On 29 August 2013, he signed a one-year loan deal with Australian A-League club Adelaide United. On 14 July 2015, Zullo signed a one-year deal with Melbourne City. On 11 May 2016, Zullo signed a two-year deal with Sydney FC. In his first season at the Sky Blues, he played an influential role as an attacking fullback, assisting three goals and forming a good partnership with left winger Milos Ninkovic. Zullo scored his first goal for Sydney FC in a 3–2 win over Wellington Phoenix. In January 2018, Zullo committed his future to Sydney FC for a further two seasons.
International career
Due to outstanding form since making his debut for Brisbane Roar, Zullo was called up for the first time for the Australia national under-23 football team before their qualifier against Iraq, in which they won 2–0. He was also a train-on player with the national U-17 squad, the Joeys, at 2005 FIFA U-17 World Championship in Peru. On 28 January 2009, Zullo made his full international debut, coming on as a substitute in a 0–0 draw with Indonesia in the group stage of qualifying for the 2011 AFC Asian Cup.
