Isometric z-soring by coordinates, not x/y

Hello, as the title implies, I want to do a z-sorting for an isometric game via i,j, sizeI and sizeJ of the objects, and not the x/y values. I don’t plan on using z axis.

I have searched google a lot and only sorting via x/y comes up.
Thus I have come, like always to Kirupa to ask for help and guidance.

If I failed to put some crucial detail to the problem don’t be afraid to ask for it, I am in dire need of help :genius:

Thank you.