Hey 
The .mview is an exported file from the rendering software Marmoset Toolbag. This file contain your assets, textures, lights, etc. in order to create a 3D viewport through websites. I don't know if you can create and share it with the trial version of Toolbag, but for this contest you can make some additionnal renders:
-If you are not uploading your model using the Marmoset viewer,
include this sheet in your final submission. This should include both
the front and back of your character in a T-pose as well as close-ups of
interesting details and areas we can't see well with the Final Image
alone. Squeeze everything you have into this one sheet.
Workflows can be a long discussion, but you can still use Zbrush to make your final renders. Texturing with polypaint and pose with transpose master is a good point. You can setup your lights in Zbrush and make some specific renders with differents materials. By mixing your images/passes in photoshop you can have a stunning result.
In other hands, a "most common" way consist to: sculpt the HD model in zbrush/mudbox/whatever, make a retopology, unwrap the UV, bake the details from the HD model and then texturing. And finally rendering.
