Zigic signed a four-year contract when he moved to St Andrew's from Valencia last summer in a £6million transfer. But the Serbia international is poised to cut short his stay, according to his agent Milan Calasan.
He said: "The only thing that is sure is that Zigic is going to leave Birmingham this summer."
Zigic struggled initially to adapt to the Premier League but gradually made an impact and scored in the Carling Cup final win over Arsenal.
He suffered groin and hip problems which ruled him out of the final third of the season although he still finished as the club's second-highest goalscorer with eight goals.
Blues have already lost the services of midfielder Craig Gardner to Sunderland for an initial £4.5million.
Stoke want to sign defender Scott Dann and striker Cameron Jerome and have made a joint £16million bid.
Goalkeeper Ben Foster is also being linked with a move to Aston Villa, where he would be reunited with former Blues manager Alex McLeish.
Source: PA
Source: PA