Complex sentence: The Legend was the result of Project XX, a joint venture Honda entered into with the Austin Rover Group of Great Britain and was mechanically related to the Rover 800 series, and the Integra was an improvement of the Honda Quint hatchback.
Split into simpler sentences: The Legend was the result of Project XX, a joint venture Honda entered into with the UK's Austin Rover Group. It was mechanically related to the Rover 800 series, while the Integra was an improvement of the Honda Quint hatchback.