The BVB director is confident the forward will remain at his current club, while stressing Robert Lewandowski will not be sold
The Germany international is continually being linked with a move away from BVB, but Zorc is confident he will stay put for the foreseeable future.
"Mario has an ongoing contract with BVB and he's feeling very well at the club and in this city. There are no signs that this will change any time soon," Zorc told Bild.
"Mario is an extraordinary player and he's still only 20. He has plenty of room for improvement."
The BVB director also had his say on the rumours linking Robert Lewandowski with a move away from the club.
"He is not for sale at any price this winter. We still have our own ambitions."
Lewandowski is under contract until June 2014.