From which book is the maxim
Zen kōan だいどうむもん "Daidō mumon"
"to achieve great understanding there is no single but thousands of ways".
“大道無門” is the first line of a verse:
This is from the introduction to 無門關, usually translated as The Gateless Barrier or The Gateless Gate, a collection of kōans by Zen master Wúmén Huìkāi (無門慧開), published in 1228. (He is perhaps better known in the West under the Japanese version of his name, Mumon Ekai.) In Robert Aitken’s translation:
The Great Way has no gate;
there are a thousand different paths;
once you pass through this barrier,
you walk the universe alone.
“大道無門” contains a pun: the author’s name Wúmén is written with the same characters (無門) as “no gate” so the line can be understood as “Wúmén’s Great Way” as well as “the great way has no gate”.
“だいどうむもん” (daidō mumon) is the Japanese pronunication of “大道無門” (dàdào wú mén).
Hideyuki Fujisawa (藤沢秀行) was a professional Go player also known for his calligraphy: presumably the writing on the fan is his work.