The Bosnian international has notched an impressive 12 Premier League goals this season, but has, on the whole, struggled to cement a regular starting berth.
After gaining a reputation for his ‘super-sub’ antics earlier in the season, Dzeko claimed that he was not happy with a spot on City’s bench.
Since then, he has been involved more regularly, but is still behind Sergio Aguero in manager Roberto Mancini’s thoughts.
This, coupled with the Italian’s criticism of his striker this term, has led to speculation that he could move on this summer, with Dortmund hopeful of luring him back to the Bundesliga.
The current German champions are set to lose Lewandowski at the end of the current campaign, and will be keen to bring in a direct replacement
Having impressed with Wolfsburg before moving to England, Dzeko is believed to meet their requirements.
The 26-year-old has already confessed that a return to Germany would interest him, but City would, likely, look to recoup most of the £27m they paid for him in 2011, which could be a stumbling block for Dortmund.
But, with the Etihad Stadium-based outfit rumoured to be interested in Lewandowski, a potential swap deal could be arranged to keep both parties happy.