^It's just a wild fan theory based on a vague similarity of the names. There was never any intention to use the Kzinti in DS9.
I personally asked Robert Hewitt Wolfe about this a couple of years back, and he confirmed that, although he may have been vaguely inspired by the sound of the names "Kzinti" and "Tsankth" (from some RPG or other, I think), he was thinking more of the dinosaur-like Hakazit from Jack Chalker's Well World series.
And the "change the name to avoid paying royalties to Niven" idea is nonsense, because we never actually
saw the aliens in question in the episode. That did happen a couple of times in early TNG novels, where felinoid aliens that were intended to be Kzinti had to have their names changed to something else; but in "The Adversary," the Tzenkethi were nothing
but a name and were never intended to be anything else. It makes no sense to assume the DS9 producers would've sought to use a name from Niven's fiction, with all the legal complications that would've entailed, for nothing more than a passing reference to an unseen species.