Complex sentence: In 1921 they moved to Paris, to escape the strictures of New York and their families' mutual dissatisfaction with their marriage, and where Gerald took up painting, and where they began to make the acquaintances for which they became famous.
Split into simpler sentences: In 1921 they moved to Paris to escape the strictures of New York and their families' mutual dissatisfaction with their marriage. In Paris Gerald took up painting, and they began to make the acquaintances for which they became famous.