The giant Serbia international, who is the club's highest earner on ?50,000-a-week, started just 13 Barclays Premier League games last term.
Is that the way to the Birmingham exit? Zigic is set to leave St Andrews
Everton are said to be interested in Zigic, while his former employer Racing Santander and Malaga are also chasing his signature.
'At the moment, the only thing that is sure is that Zigic is going to leave Birmingham this summer,' the player's agent, Milan Calasan told Serbian newspaper Sport.
On target: Zigic scored eight goals last season
'There is still a long time left to decide, so we are not in a rush. Nikola's wish is to continue his career in England or Spain.'
Zigic last played in Birmingham's 2-1 win over Bolton at the beginning of April.
But the 30-year-old struggled with hip and groin injuries, and was unavailable for the Blues ill-fated run-in.
Zigic heading for Birmingham exit as club makes cuts following relegationZigic set for new fitness regime as giant striker bids to feature in final games Explore more:Places: Birmingham, Spain, United Kingdom