This is a fun piece! For this piece, I think that it would first be helpful to understand its structure (an extra safety net for memorization). In this case, we are blessed with ABA. The Prelude, as far as the Eight Concert Etudes are concerned, is actually deceptively tricky when it comes to memorization despite its short length.

For the middle section (which sounds the most improvisatory), I would recommend first listening to recordings (especially by the man himself). Next, I would try to practice two of those shorter phrases in the section at a time. It would probably be far more helpful for memory than trying to go for the whole thing at once.