Complex sentence: Chandler is amazed at how well Phoebe's break-up goes, while he accidentally pokes Janice in the eye and endures what he claims as "the worst break-up in the history of the world".
Split into simpler sentences: Chandler is amazed at how well Phoebe's break-up goes, while he struggles with his own. He accidentally pokes Janice in the eye, and endures what he claims as "the worst break-up in the history of the world".