I have a pretty good vocabulary. I don't use any of these words. I think I recognize three of them as words I might have seen: fanfaronade, xenization, zugzwang. I might be able to guess the right meaning on a multiple-choice test but in reality I don't know them--I'd have to look them up. If I had a chance to use them playing Scrabble or Anagrams, I would certainly use them--wait--a Scrabble set only has one "z." Otherwise, you don't need to have these words in your passive vocabulary because if you run into them you can look them up, and you don't need to have these words in your active vocabulary because there's perhaps an 0.01% chance that your listeners will understand you if you use them. It's pretty much a matter of argument whether you can all any of these "real words." Every lexicographer has to make arbitrary decisions about cutoffs, and where the boundary of the language ends. Is "fanfaronade" something like "braggadocio?" Checking... yes. OK, give me a point for that. I thought "zugzwang" was something in quantum physics but, nope. "Xenization" sounds like deporting someone, making them foreign? It's not in Merriam-Webster's Third Unabridged, I say it isn't a word. I don't think I've ever seen it after all, I think I was thinking of "xerification." "Gorgonize" sounds like it means to turn something into a gorgon like Medusa? No, it means to paralyze them like the sight of Medusa did.

I checked your words in the online Oxford dictionary. Only "zugzwang" (a technical word in chess) and "fanfaronade" were in the dictionary. So I would safely ignore the others as not even Oxford can help us understand them!

Let's consider a few angles, as follows: 1. Good contemporary writing. Is good contemporary writing founded on using infrequently used words? No. Simple English can be very elegant and powerful and is thankfully now fashionable among intelligent educated people. 2. Do people use these words? Some. Very few. 3. Do people understand them? Most people do not. 4. Who may use these in good natural style in their writings? One wonders. Perhaps the late Bernard Levin. Perhaps you? Perhaps some newspaper columnists that you admire? Lex in the Financial Times? Perhaps a university don that you know? Most top students can slip one or two of these words in without appearing to be pretentious or destroying their writing style. 5. Are they accepted in exams? Why not? It is a high risk activity, however. How confident are you that you can weave these words seamlessly into a well-written essay? 6. Is it a mark of scholarship or learnedness to use these words? Not particularly. 7. What is the point of these words? They may be entirely apt in certain contexts. I think that is all we need to consider at this point in time.

I think the adjective you need for these words is "obscure" and not "old".