Willem was born in Amsterdam. He joined the Dutch navy at a young age and had risen to the rank of captain by 1652. He took part in the First Anglo-Dutch War from 1652–1654, fighting in the Battle of Dungeness on the Prinses Aemilia, and on the Campen (after the previous captain, his brother Joris van der Zaan, had been killed in the Battle of Portland; in the same battle his other brother, Huybrecht van der Zaan, was killed also) in the Battle of the Gabbard and the Battle of Scheveningen. In 1655 he was made a full captain. In 1656 he commands the Zuyderhuys, having on board his nephew, the son of Huybrecht, Cornelis van der Zaan, later a captain also. In 1657 he participated in an action in the Mediterranean under Vice-Admiral Michiel de Ruyter, during which he captured the French warsh