Culling z-axis curves for a 12-curve box

[DP]

I have a Brep wireframe that breaks it down into 12 curves. I am
trying to figure out how to cull all x,y axis curves and simply select
the z-axis curves. I have tried extracting end points and decomposing
the points, but that seems to be a dead end. Does anyone have any
insight? Thanks in advance!