What AssertnFailure said makes sense. If I call someone myopic, in literal terms I'm calling him near-sighted. What I figuratively mean is that he's managed to miss an important detail.
I don't believe that Zabuza ever claimed to be the strongest of the seven swordsman from Mist. Zabuza was a cruel individual, and he thought he was very smart, but he never claimed to be anything beyond jounin in strenght. He even said that Haku could probably beat him.