The inscription is a saying of the Sixth Patriarch, so the inference here is that the Zen insight of the Indian Patriarch Daruma was passed on to the Chinese Sixth Patriarch Eno and that spirit is captured in paper with brush and ink by the Japanese abbot Daikyu (and that zenga is now in the West to inspire us).
Daikyu was Dharma heir of Shaku Soen, the master who introduced Zen to the West. Daikyu was abbot of just about every Rinzai head temple, serving as abbot of Engaku-ji, Myoshin-ji, and then primate of all thirteen Rinzai schools when they were briefly united as one entity. Daikyu's zenga have an impish, humorous quality.