Complex sentence: In 2001, team Penske marked its return to the Indy 500 after a five-year absence due to the open wheel split, after the 1995 PPG IndyCar World Series season.
Split into simpler sentences: In 2001, team Penske marked its return. To the Indy 500, a five-year absence was due to the open wheel split, after the 1995 PPG IndyCar World Series season.