Complex sentence: Rački doc.434 This proves that Croatia was in bad relations with the Byzantine Empire at that time, and once the emperor "Basil II" had died in 1025, Krešimir stopped paying tribute to the empire.
Split into simpler sentences: Rački doc.434 This proves that Croatia had poor relations with the Byzantine Empire at that time. After the death of Emperor Basil II in 1025, Krešimir stopped paying tribute to the empire.