Former Chelsea forward Zola had previously managed West Ham United and Watford in England, but it was still a surprise when he was appointed in December after Birmingham sacked Gary Rowett with the club in seventh place in the league and well-positioned to make the promotion playoffs.
And fears over Zola's suitability for the role seemed justified as the Blues slipped down the table rapidly in the months that followed the Italian's appointment.
And with City in 20th place after Monday's loss to Burton Albion, the club announced Zola's resignation on Twitter.
"I am sorry because I came here with a lot of expectations and the results haven't been good. I take full responsibility for that," Zola told a news conference.
Read the full article on eurosport.co.uk: Zola resigns as Birmingham slip close to drop zone