Complex sentence: The game is the fourth main installment (sixth overall) in the "Crash Bandicoot" video game series, and the first not to be developed by Naughty Dog.
Split into simpler sentences: The game is the sixth instalment in the "Crash Bandicoot" video game series. It is the fourth in the main series of the franchise, and the first of those not to be developed by Naughty Dog.