I'd say they were approximately equal. The Schulz-Evler calls for a lot of chordal and octave stamina; the hardest thing in the Cziffra is imo the velocity of the myriad runs whilst keeping them quiet. The lh is harder in the Schulz-Evler whereas I think the rh is more tested in the Cziffra. What is hardest is having enough technique to play them with room left over for panache and style! As a footnote, this Cziffra is far more accessible some of his others, like the Bumblebee, Tristch-Tratsch, Fantasie Roumaine or William Tell.