Here I'll show how I worked to make my first learning project using ZBrush.

First, I took some images to use as reference for the work. Then, I modelled a base mesh in Blender, and give to the mesh a subsurf effect, to make it a little smooth.

After that, I marked the mesh to build the uv map, that I would use later.
Then, I imported the mesh to Zbrush to sculpt the face, muscles and the suit. Finishing this step, I use the uv map and took a testing render of the model.
With the model ready, it's time to pose. For this, I used the Transpose tool. After that, I took the final render of the model, and some renders to compose the lighting of the scene, later.
I modelled too some kind of rock, to compose the scene.
Finally, I mix everything in Photoshop, using a sky photo from the background.
Then, I made some lighting effetcs and...
... after work with the colors, the scene is done.