A sorting description

I would like to describe a sorting process of "faces". The sorting criteria is the z axis value of each face. The face which has minimum z value comes first, and the minimum z value of the face is used just if two faces have the same maximum z value, then the one with the highest minimum z value comes first.

I am not sure how to write it in a academic way.

Please, is there any suggestion?

Also, is it right to say "The sorting criteria"?