ἐπεὶ δὲ σκοπῶν οὐ δύναμαι οὔτε σὲ αἰσθέσθαι πειρώμενον ἡμᾶς κακῶς ποιεῖν ἐγώ τε σαφῶς οἶδα ὅτι ἡμεῖς γε οὐδὲ ἐπινοοῦμεν τοιοῦτον οὐδέν, ἔδοξέ μοι εἰς λόγους σοι ἐλθεῖν.
Since, when reflecting, I cannot perceive that you are trying to hurt us, and since I know for sure that we are not planning anything like that either, it seemed proper to me to hold a parley with you. The clause ἐγώ τε σαφῶς οἶδα ὅτι still depends on ἐπεὶ, I think, so why does the CGCG translate as following? “However, my investigations have produced no evidence that you are trying to injure us and I know for sure that we have no such schemes in mind either. So I wanted to talk things over with you.”
Cf., Brownson’s translation: But since, upon inquiry, I am unable to ascertain that you are trying to do us harm, and am perfectly sure that we, for our part, are not even thinking of any such thing against you, I resolved to have an interview with you,
The CGCG translation simply makes a separate sentence of the ἐπεὶ clause. “So” in its second sentence corresponds to Xen.'s introductory ἐπεὶ. (“Since I can’t …, I decided …” > “I can’t …. So I decided …”)
Incidentally, I think you misunderstand the οὐδὲ, which applies to ἐπινοοῦμεν (“not even”).
That οὐδὲ follows the οὔτε doesn’t it?
No, the οὐδὲ is altogether independent of the οὔτε. It’s the τε that’s paired with the οὔτε, so that we have two coordinated halves, negative and positive respectively. But the structure is not entirely balanced, for οὐ δύναμαι (unlike the opening ἐπεὶ δὲ σκοπῶν) does not carry over to the second limb (ἐγώ τε σαφῶς οἶδα etc.). It’s as if he decided to add the second limb only after he’d already said οὐ δύναμαι. At that point the οὔτε commits him to a second limb. Like all but the most formal writers, Xenophon doesn’t care for perfect symmetry.