Complex sentence: Winning the Coupe de France ensured Auxerre qualified for the UEFA Cup where Lachuer scored his first goal in European competition, to go alongside the 3 league goals he amassed as Auxerre finished 4th in Ligue 1 to qualify for the UEFA Cup for the second successive season.
Split into simpler sentences: Winning the Coupe de France ensured Auxerre qualified for the UEFA Cup where Lachuer scored his first goal in European competition, to go alongside the 3 league goals he amassed as Auxerre finished 4th in Ligue 1. In doing so they managed to qualify for the UEFA Cup for the second successive season.