Complex sentence: The breed was principally known for two traits, they had a pacing gait that was easy to sit, and they were hardy, sure-footed, and full of power, and they were docile and easy to handle.
Split into simpler sentences: The breed was principally known for two traits, they had a pacing gait that was easy to sit. They were hardy, sure-footed, powerful, yet docile and easy to handle.