Zadkovich can play in midfield or at right-back and is currently training with the Rams as he tries to earn a contract at Pride Park.
He recently had a trial with Crystal Palace and spent two seasons in England as a teenager, firstly with QPR and then at Notts County.
The Australia Under-23 international found the net once in nine appearances for Notts in the 2004-05 season before returning to his homeland.