And how will you debate a flat earth Zetetic, when their approach is to reject dogma and you aren't able to accomplish that?
Rather than asking how they might debate, why not debate them and find out?
As well, I think it's pretty clear that Zetetics are not much for rejecting dogma, actually quite rooted in it, you know, holy scriptures and such:
"The founding meeting of the Universal Zetetic Society was apparently held on Wednesday, September 21, 1892, at John Williams’s Southwark home. [ref. 4.2] It’s not clear who besides Williams attended, though probably most of those selected to the UZS Committee were there. The founders decided on a name, a motto, an object, and a set of rules as follows:
OUR MOTTO
For God and His truth, as found in Nature and taught in His Word.
OUR OBJECT
The propagation of knowledge relating to Natural Cosmogony in confirmation of the Holy Scriptures, based upon practical investigation."