Boundless wind and moon—the eye within eyes,
Inexhaustible heaven and earth—the light beyond light.
The willow dark, the flower bright—ten thousand houses;
Knock on any door—someone will answer.
– Preface to the Blue Cliff Record
John Tarrant talks about the bond between Daoism and Chan Zen. See transcription with same name :https://www.pacificzen.org/library/knock-on-any-door-daoist-masters-zen-koans/