How did Confucian ideas and Zen practices become connected during Japan's Edo period?

During Japan’s Edo period (1603–1867), the connection between Zen and Confucianism deepened as both traditions cooperated with the Tokugawa shogunate to regulate society and maintain political stability.1

The integration of these traditions occurred through several key developments:

• Shared Moral Frameworks: Zen monks taught a form of conventional morality (tsūzoku dōtoku) that was heavily influenced by Confucian values. Buddhist teachings were frequently utilized to justify the strict social hierarchy enforced by the government.1
• Contemplative Practices: Confucian teachers adopted Zen Buddhist meditation techniques, adapting them into a practice known as "quiet sitting" (seiza), which served as a Confucian contemplative method.1
• Blurred Distinctions: As a result of these exchanges, the social and religious boundaries between Zen practice and Confucianism became increasingly indistinct.1

While Zen monasteries had previously served as centers for importing Chinese arts and Neo-Confucianism during the medieval period, the Edo period shifted the focus toward using these philosophies to reinforce state order and social ethics.12