回答:
man zshall
/forward-word
/backward-word
echo $WORDCHARS
*?_-.[]~=/&;!#$%^(){}<>
WORDCHARS='*?_-.[]~=&;!#$%^(){}<>' ;# without /
WORDCHARS=${WORDCHARS//[\/]}
です。
WORDCHARS=${WORDCHARS/\/}
WORDCHARS=$WORDCHARS:s:/: