Timur killed more Muslims than non-Muslims.  His stated piety was usually an excuse.  It is true that he paid special attention to non-Muslims on occasion.  He attacked Georgia a record six times.  His planned attack on China was justified in religious terms.  He attacked Smyrna (modern Izmir) just to defeat the Crusaders in Anatolia  and yet, curiously, he made no attempt on Constantinople, also in Anatolia and the seat of the Byzantine Christian empire.