Complex sentence: While Murad was preoccupied in the Balkans, he named as his commander-in-chief in Anatolia a renegade Greek, Halil Yakhshi, a brother-in-law of the vizier Bayezid Pasha, who had been executed on Junayd's insistence.
Split into simpler sentences: While Murad was preoccupied in the Balkans, he named as his commander in Anatolia a renegade Greek, Halil Yakhshi. Halil was brother-in-law of the vizier, Bayezid Pasha, who had been executed on Junayd's insistence.