"Well-makers lead the water (wherever they like); fletchers bend the arrow; carpenters bend a log of wood; wise people master themselves." What central part of Buddhism expressed in the quote appealed to samurai who practiced Zen?

Self control and discipline are expressed in this quote

Explanation:

The essence of Zen is attempting to understand the meaning of life directly, without being misled by logical thought or language. Self discipline and control are central part of Buddhism and the first step is to control one's  mind through meditation and other techniques that involve mind and body; to give up logical thinking and avoid getting trapped in a spider's web of words.

the effect of the ming leaders banning ships with more than two masts was that there was no further construction of ships masts, because there was a surplus. ming emperors disallowed foreign exploration

i think it was   tsar alexander ii