Complex sentence: As a defense against the Incas the Andean chiefdoms of Ecuador formed alliances with each other which historians of that region call the Quito Confederation with the Kingdom of Quito the leader of this confederation.
Split into simpler sentences: As a defense against the Incas the Andean chiefdoms formed alliances with each other. Historians of that region refer to these alliances as the Quito Confederation with the Kingdom of Quito being the leader of this confederation.