MF Doom (MC) and Madlib (beats) are Madvillain. Their 2004 album "Madvillainy" included a Zappa sample. Track 3, 'Meat Grinder', starts with a repeated 'Sleeping In A Jar' sample.
I learned earlier today that 2004 also saw the release of "Madvillainy Instrumentals", a 2LP instrumental version of the album. It got released in a generic sleeve on the same label (Stones Throw Records).
This instrumental album got rereleased in 2011. This time with artwork / an album cover.Both of these albums include the Zappa sample.
Here's the data, including album covers: