"Zen seven, ken three" is a samurai saying that you hear in a martial arts dojo (training hall) even today. It means that technical ability with the sword (ken) or any other weapon is only 30 percent responsible for your success or failure.
The 70 percent factor (the Zen of the saying) in any battle—crossing swords in kendo, or solving a problem—is inside you. Inner training is devoted to cultivating that inner power.