Complex sentence: He finished school and was discovered by one of the founders of The Second City in Chicago, which he joined in 1964, performing with the likes of Robert Klein, Fred Willard, Peter Boyle, and Joe Flaherty.
Split into simpler sentences: He finished school and was discovered by one of the founders of The Second City in Chicago, which he joined in 1964. There he performed with the likes of Robert Klein, Fred Willard, Peter Boyle, and Joe Flaherty.