Complex sentence: She also helped to maintain good relations between Navarre and Castile, and much noble Castilians including the Duke of Benavente and members of powerful families Dávalos, Mendoza and Zuñiga settled in Navarre.
Split into simpler sentences: She also helped to maintain good relations between Navarre and Castile. As a result of the good relations, members of the Castillian nobility including the Duke of Benavente and members of the powerful families of Dávalos, Mendoza and Zuñiga settled in Navarre.