Complex sentence: She is also noted for her duet with Robert Plant on the song "The Battle of Evermore" from Led Zeppelin's fourth album released in 1971, and Denny remains the only guest vocalist on a Led Zeppelin album.
Split into simpler sentences: She is also noted for her duet with Robert Plant on the song "The Battle of Evermore" from Led Zeppelin's fourth album released in 1971. She remains to this day the only guest vocalist on a Led Zeppelin album.