Complex sentence: Their biggest hit was a cover of The Skyliners' 1959 recording "Lonely Way", which they recorded in 1963 and backed with "Your Way" on Mellomood Records.
Split into simpler sentences: Their biggest hit was a 1963 cover of "Lonely Way", The Skyliners' 1959 recording. They followed it up with "Your Way" on Mellomood Records.