zip_view::iterator's operator<=> is constrained with (three_way_comparable<iterator_t<maybe-const<Const, Views>>> && ...). This is unnecessary, because the comparison is performed on the stored tuple-or-pair, and both std::tuple and std::pair provide operator<=> regardless of whether the elements are three-way comparable.

Note that, because neither std::tuple nor std::pair provides operator< since C++20, comparing two zip::iterators with operator< (which is specified to return x.current_ < y.current_, where current_ is a tuple-or-pair) eventually uses tuple or pair's operator<=> anyway.

Thus, I think it's possible to make operator<=> not require three_way_comparable. This also makes it possible to remove the operator functions for <, >, <=, >= and rely on the operators synthesized from operator<=>.