Van Dyke Parks was part of The Mothers fir a very short time (pre-"Freak Out"). He did play with various Zappa alumni afterwards, and his compositions were performed by Jimmy Carl Black, among others.
Last year the Bananastan label released 6 singles by Van Dyke. I can't tell you anything about the music, but the artwork is stunning.
Here are some covers & back-covers of the series.
Pictures and extra data have been added to the U.M.Archives.