Lot departed from Zoar and lived in the mountains along with his two daughters, because he was afraid to live in Zoar. Instead, he and his two daughters lived in a cave.
References for Genesis 19:30
Then the firstborn said to the younger, "Our father is old, and there is no man in the land to sleep with us [as is] the custom of all the land.
Come, let's get our father to drink wine so that we can sleep with him and preserve our father's line."
So they got their father to drink wine that night, and the firstborn came and slept with her father; he did not know when she lay down or when she got up.
The next day the firstborn said to the younger, "Look, I slept with my father last night. Let's get him to drink wine again tonight so you can go sleep with him and we can preserve our father's line."
That night they again got their father to drink wine, and the younger went and slept with him; he did not know when she lay down or when she got up.
So both of Lot's daughters became pregnant by their father.
The firstborn gave birth to a son and named him Moab. He is the father of the Moabites of today.
References for Genesis 19:37
The younger also gave birth to a son, and she named him Ben-ammi. He is the father of the Ammonites of today.
References for Genesis 19:38