Complex sentence: They are placid in their fatalism, and patiently explain their philosophy to Billy Pilgrim during a stint he spends caged in a Tralfamadorian zoo; eventually he adopts their attitude, is returned to Earth, and tries to spread their philosophy.
Split into simpler sentences: They are placid in their fatalism, and patiently explain their philosophy to Pilgrim during the interval he spends caged in a Tralfamadorian zoo. Eventually Pilgrim adopts their attitude, is returned to Earth, and tries to spread their philosophy.