Complex sentence: His career began when he starred as Bruno in the 1966 film "Mademoiselle", and more notably perhaps in Franco Zeffirelli's 1968 film "Romeo and Juliet" as Balthasar, Romeo's manservant and trusted friend.
Split into simpler sentences: His career began when he starred as Bruno in the 1966 film "Mademoiselle". In 1968, he was cast in Franco Zeffirelli's adaptation of "Romeo and Juliet" as Balthasar, Romeo's manservant and trusted friend.