Complex sentence: After the overthrow of the Byzantium in the Fourth Crusade by the Venetians and Franks in 1204, was definitively conquered by the Venetians under the leadership of Marco Sanudo and as part of the Duchy of the Archipelago, Syros would remain under Venetian rule until 1522.
Split into simpler sentences: After the overthrow of Byzantium in the Fourth Crusade by the Venetians and Franks in 1204, the island was definitively conquered by the Venetians under the leadership of Marco Sanudo. As part of the Duchy of the Archipelago, Syros would remain under Venetian rule until 1522.