Complex sentence: The Zu-Vendi are a warlike white race entirely isolated from other African races and when Curtis and Quatermain's party arrives are ruled jointly by two sisters, Nyleptha and Sorais.
Split into simpler sentences: The Zu-Vendi are a warlike white race isolated from other African races. At the time of the British party's arrival, they are ruled jointly by two sisters, Nyleptha and Sorais.