Complex sentence: Also the Byzantine Empress Irene called herself "basileus" (βασιλεύς),'emperor', rather than "basilissa" (βασίλισσα),'empress' and Jadwiga of Poland was crowned as "Rex Poloniae", "King of Poland".
Split into simpler sentences: Also the Byzantine Empress Irene called herself "basileus" (βασιλεύς),'emperor', rather than "basilissa" (βασίλισσα),'empress'. And Jadwiga of Poland was crowned as "Rex Poloniae", "King of Poland".