For this image I used Zbrush to create building structures. I made a base variant and then used the ZBrush 2018 project deformers to add variation to the buildings. I also used ZBrush to create a quick rock structure that I could reuse in the scene. I used Worldmachine to make terrain that I could use for the larger parts of the terrain. Everything was rendered in Maya Arnold using multiple passes and I used those elements to comp together in Photoshop for the final image.