Complex sentence: Oberon orders Puck to keep Lysander and Demetrius from catching up with one another and to remove the charm from Lysander so Lysander can return to love Hermia, while Demetrius continues to love Helena.
Split into simpler sentences: Oberon orders Puck to keep Lysander and Demetrius from catching up with one another and to remove the charm from Lysander. So Lysander can return to love Hermia, while Demetrius continues to love Helena.