Final answer:
Rhea stopped Kronos from swallowing Zeus by giving him a stone to swallow, thinking it was his son. This allowed Zeus to grow up and later overthrow Kronos.
Step-by-step explanation:
Rhea planned to stop Kronos from swallowing her children by deceiving him. When her youngest child, Zeus, was born, Rhea hid him away on the island of Crete and gave Kronos a stone wrapped in swaddling clothes to swallow instead. This stone, known as the Omphalos stone, was swallowed by Kronos who thought it was his son.
This ruse allowed Zeus to grow to maturity without the threat of his father, Kronos, consuming him. Later, Zeus would lead a rebellion against Kronos and the Titans, ultimately defeating them and liberating his siblings, who had been swallowed by Kronos but remained alive inside him.