Zeteticism, if properly followed, would lead to disbelief in a flat earth because it's the philosophy of only believing what your senses tell you, and not accepting data from mechanical or electronic or third party sources. Since your senses tell you you can only see a few miles to the horizon at sea that means a true zetetic would conclude the earth could not be flat, as a flat earth would not have a horizon such as that.
Im not a flatearther though but thats what zeticism is as far as I can tell.