Zbrush is one of the industry standard sculpting programs used for high resolution modeling/detail for both film and games. Many visual effects and game studios use it, from Weta Digital, ILM to Valve and many many others. If you are a modeler and don't know how to use Zbrush you pretty much can't get a job.
The image is pretty well done, if you look at the thread you can see the exact reference image he used and how different his model/render is compared to the original picture.
