Complex sentence: Zach walks home and discovers his family members shocked by the sudden reappearance of his dead grandfather, closely followed by the previous owners of the house; at the same time, an emergency broadcast reveals the zombie apocalypse is not far at hand.
Split into simpler sentences: Zach walks home, only to discover that his dead grandfather has resurrected, closely followed by the previous owners of the house. An emergency broadcast reveals the zombie apocalypse is not far at hand.