Just a suggestion..the sentence might make better sense this wayBoth the fisherman and the woodcutter were disciples of a well-known expert; their martial arts were nothing but ordinary.
These two sentences comvey exactly opposite meanings..by analogy,consider the following two sentences a)he speaks nothing but the truth. b)He speaks anything but the truth. Again, exactly opposite meanings.Both the fisherman and the woodcutter were disciples of a well-known expert; their martial arts were anything but ordinary.
Thanks so much for the translation!! Its a really exciting part of the story.