Well, usually you get things right, but I'm afraid that not this time. No, 'tego' is not any Nominative form. Masculine singular Nominative is "ten". And it's masculine singular inanimate Accusative as well. You're right with the animate one.
Unless you actually meant Genitive? Cause we have Genitive here, and I don't know why mention Nominative.
'"Znamy tego X" means "We know this X". With a masculine singular X. "We know this" would be "Znamy to". Because such 'this' can only be a dummy pronoun, not anything specific. And the dummy pronoun is neuter.
Also, frankly, the only context when it makes sense with "znać" that comes to my mind would be "Yeah, we are familiar with such situation(s)" or "Yeah, we are familiar with such behaviour"... otherwise, it shoud be "wiedzieć". "Wiemy to" = We know that. We have this knowledge. We are aware of it.
"Tego nie znamy" would sound rather unusual. "My tego nie znamy" is already a lot better, but still I'd go for "My nie znamy tego". "this" is the new information, it shows what you actually don't know.
Moreover, I don't like this sentence at all. "znać" is "to know" as in "to be familiar with". With such a vague sentence, "wiedzieć" (Nie wiemy tego as simple We don't know that, we don't know what the answer is) seems a lot more probable.