Complex sentence: Aside from the "Odyssey" and the "Iliad", the cyclic epics only survive in fragments, the most important of which is a detailed summary written by someone named Proclus (not same person as the philosopher Proclus Diadochus).
Split into simpler sentences: Aside from the "Odyssey" and the "Iliad", the Cyclic Epics only survive in fragments. A summary of their contents survives, written by someone named Proclus (not same person as the philosopher Proclus Diadochus).