Embarrassed to ask another question about this text so soon, but I'm confused by the presence of both εἰπεῖν and εἰρήκασιν in this clause. I believe that both verbs mean "to say", or something like that, yet I'm not sure why they belong together here, or why one is conjugated and the other infinitive. It seems one would suffice.
καίτοι ἀληθές γε ὡς ἔπος εἰπεῖν οὐδὲν εἰρήκασιν.
I also don't see how the rest of it fits together. I believe ἀληθές is an adjective meaning "true", ἔπος a noun meaning "word", and οὐδὲν an adjective meaning "not one". Yet these three words which seem to belong together ("not one true word") are separated by other words. How do all these parts work together?