The 28-year-old player played for Sarajevo last season.
Ziljkic started his playing career in 2015 in Donji Srem and has also played in Serbia’s Novi Pazar, Bosnian teams Gorica, Sloboda Tuzla, Tuzla City, and Borac Banja Luka and Slovenian team Olimpija Ljubljana.
Esteghlal has previously completed the signing of Milad Zakipour, Mohammad Hossein Eslami, Ramin Rezaeian, Saman Fallah and Alireza Koushki.