Complex sentence: At Feyenoord, Jansen won four League Championships, one Dutch Cup, one UEFA Cup, and the European Cup in 1970 when Feyenoord defeated Celtic 2--1 in Milan.
Split into simpler sentences: At Feyenoord, Jansen won four League Championships, one Dutch Cup, and one UEFA Cup. He also won the European Cup in 1970 when Feyenoord defeated Celtic 2--1 in Milan.