Your ignorance is quite disturbing; as is your quintuple post.
Well, to tell the truth, Mazeppa IS harder than any of the Chopin Etudes. ANd Mazeppa isn't even Liszt's hardest etude.
Proof:
Here are Chopin's known Etudes:
Op. 10 nos. 1-12
Op. 25 #1-12
3 New Etudes
Here are some of Liszt's harder Etudes (because we're talking about that sh!t topic named hardness):
Douze Grandes Etudes
Transcedental Etudes: Mazeppa; Feux Follets; Wild Jagd; Chasse-neige
The First Version of the Paganini Etudes
La Campanella (well, not as hard as the Etudes listed above, but still, it's harder in a way than Chopin's Etudes

)
Also, even though Unn Sospiro is more for the "intermediate pianists" and Chopin's are more for the "advanced", when I actually think about it, Un Sospiro is harder than most Chopin Etudes technically.
Proof:
Op. 10 #1, 2, 4, 11; Op. 25 #6, 11;
Those are the Etudes that even STAND A CHANCE in comparing to Un Sospiro in technical difficulty. OK, maybe Op. 25 #6 is harder, though
