maximum distance between points no vertical match

Hi, I have several lists of points organized in branches, in different levels, and I want to select one point per branch so that they are separated as much as possible and their (z) values don´t match if the points selected are placed in consecutive levels (say from jpg 1 to jpg 2).

So far, I have tried voronoi, delaunay, populate 2D and proximity 3D, with no success I have to say...

THX