Final answer:
Due to Zeus's pity for Cadmus and Harmonia's hardships, he transformed them into serpents, as a sign of his compassion and to provide them with a new form of existence.
Step-by-step explanation:
Zeus, in Greek mythology, often takes actions that reflect his emotions and the dynamics of the gods. One well-known myth involving Zeus's compassion involves Cadmus and Harmonia. The story goes that after enduring many hardships and cultivating the city of Thebes, Zeus felt pity for them in their old age. To ease their suffering, Zeus transformed Cadmus and Harmonia into serpents, allowing them a different form of life, possibly one free of the toils of human existence.