Which of the following is zero over lapping of orbitals; if z-axis is inter nuclear axis

i) If z-axis is internuclear axis, then in between the s-orbital and px-orbital overlapping not at all possible. Since, s-orbital always forms σ-bond, that should be with pz orbital only.ii) pz involves in σ-bond & hence px, py must form π-bond . π-bond is not possible with "s" orbital.