You can take a bus from Mostar to Prizren via Podgorica in around 12 h 34 min.
How to get from Mostar to Prizren
From Mostar Bus Station East bus to Podgorica then bus to Prizren. 12 h 34 min 39€. From Mostar bus to Nevesinje, bus to Bar, then bus to Prizren. 14 h 7 min 46€. From Mostar drive to Prizren. 6 h 59 min 39€.