The 22-year-old, who signed for Derby in April, played at right-back for the Socceroos in their surprise 1-0 World Cup qualifier defeat to China.
He has been included in the Australian squad before but Sunday's match in Sydney in front of 70,000 fans was his first appearance.
"I thought I did all right," Zadkovich told the Derby Evening Telegraph."
"I had shivers when I was singing the national anthem. Wearing the Australian shirt was the proudest moment of my life.
"It really was a special feeling, a priceless experience. It was just a little taste. I want to play as many times as I can."
Zadkovich was one of four Socceroos making their first starting international appearance.
"Pim Verbeek didn't play us for charity - we're the next generation of Australian players and he wanted to have a look at us," he said.
"Hopefully I can stay in the team for the next stage of the qualifiers - I can only train my hardest and show I can do the job.
"I'll have to be patient, there are some great players in front of me."