His wife was Bosa, daughter of Leka Dukagjin who was a father ofTanush Major Dukagjini. Their children were Lekë Zaharia, Bolja and a daughter of unknown name who married Đurađ Đurašević Crnojević. Koja died sometime before 1442. According to Ćiro Truhelka Bolja Zaharia was married to Petar Vojsalić, while according to Aleksa Ivić she was married to Petar I Pavlović. Koja's widow Boša died in Scutari on 19 September 1448 when a lot of people died during a fire in the town.
Until 1395 Koja Zaharia was castellan of Sati, which belonged to a fief of Konstantin Balšić and was part of the Lordship of Zeta under Đurađ II Balšić. In 1395 Balšić ceded Sati together with Scutari and Drivast to the Venetian Republic, but Zaharia refused to allow the Venetians to take control over Sati.
Ottoman Empire
When Koja captured the castle of Dagnum in 1396 he proclaimed himself the Lord of Sati and Dagnum and from there he ruled the territory around it as an Ottoman vassal. In October 1400 Koja proposed to the Venetians to simulate a battle in which he and his cousin Dhimitër Jonima would pretend to lose their possessions to the Venetians, in exchange for provision of 500 ducats annually. The Venetians did not promptly respond and Koja returned to the sultan. In 1402, together with other Albanian noblemen, he fought alongside Bayezid I forces, in the Battle of Ankara.
In 1403, a year after the Ottomans were defeated in the Battle of Ankara, Koja together with his vassal Dhimitër Jonima accepted Venetian suzerainty. During the First Scutari War between Zeta and Venetian Republic, he supported Venetian forces. Around 1412, Koja's daughter Bolja married Balša III and in return Balša III allowed him to administer Budva. At that time Koja's other daughter was already married to a member of Đuraševići who held the most distinguished position in Balša's court. To bring Koja even closer, Balša appointed him as castellan of Budva. After the death of Balša III, Koja's daughter Bolja together with her two daughters returned to her family in Dagnum. Koja Zaharia supported Serbian despot Stefan Lazarević until he was defeated by Venice in December 1422. Although Venetian admiralFrancesco Bembo offered money to Gjon Kastrioti, Dukagjins and to Koja Zaharija in April 1423 to join the Venetian forces against the Serbian Despotate, they refused. In one period Serbian despot Stefan Lazarević intended to financially destroy Koja Zaharia and ordered Ragusan traders to avoid paying taxes to Koja and to travel to Serbia via Lezhe not through Koja's Dagnum.
Ottoman Empire
When Ishak Bey captured Dagnum from Koja Zaharia in 1430 it was attached to the territory controlled by Ali Beg, while Koja was either imprisoned or expelled. After the Albanian Revolt of 1432–1436 was crushed the sultan entrusted Koja's son Lekë Zaharia with a position of Dagnum's governor.
