  For a link with zero determinants, a Z-coloring is defined as a
generalization of Fox coloring. We call a link having a diagram which admits a
non-trivial Z-coloring a Z-colorable link. The minimal coloring number of a
Z-colorable link is the minimal number of colors for non-trivial Z-colorings on
diagrams of the link. We give sufficient conditions for non-splittable
Z-colorable links to have the least minimal coloring number.
