Complex sentence: He reached the quarterfinals at the US National Championships in 1918, and at the tournament now known as the Cincinnati Masters he was a singles finalist in 1911 and a quarterfinalist in 1910.
Split into simpler sentences: He reached the quarterfinals at the US National Championships in 1918. At the tournament now known as the Cincinnati Masters, he was a singles finalist in 1911 and a quarterfinalist in 1910.