Complex sentence: He joined SEAT's SEAT Sport team in 2004 for the European Touring Car Championship (ETCC), and the World Touring Car Championship (WTCC) when this replaced it for 2005.
Split into simpler sentences: He joined SEAT's SEAT Sport team in 2004 for the European Touring Car Championship (ETCC). SEAT and Rydell continued in the World Touring Car Championship (WTCC) when it replaced the ETCC for 2005.