Build your strength. The piece is something of an endurance test. You cannot put cuts in it. You can practice it as block chords a good part of the time. Ibert’s Reflet dans l’Eau is even longer. Hasselman’s Prelude is wonderful and gives you the reverse pattern, of upward arpeggios, but with very wide spacing. So, figure out how much you can practice without fatigue, and do that much each day, changing sections, and when you have it up to tempo, you’ll be able to put it all together. It’s not logical to try to play through the whole piece in a slow tempo. Exercising your arms with weights is also very helpful in building strength, stamina and endurance. It is a professional piece, though used widely by students.