Boss Dario Gradi said: "We have someone else wanting to take him and hopefully that will suit Calvin."
The 25-year-old has made six appearances for the Railwaymen this season but is not in Gradi's first XI and has been given permission to leave temporarily.
Explaining a decision not to join Southend United, Zola said: "I have a young family and if I move it has to be right for them as well."
The Kinshasa-born frontman netted 18 times last season.