Complex sentence: Some would also keep the Latin forms of their surnames, as Latin was the official language of the Kingdom of Poland, hence the popularity of Late-Medieval or Early-Modern forms such as "de Zamosc Zamoyski".
Split into simpler sentences: Some would also keep the Latin forms of their surnames, as Latin was the official language of the Kingdom of Poland. Hence the popularity of Late-Medieval or Early-Modern forms such as "de Zamosc Zamoyski".