Does ZBrush and Mudbox work like the sculpt tool in maya?

Or is it different?

It kind of seems like drawing might be the most valuable skill in Maya because it seems like drawing the template images and being able to workout how the lines should be diagramed in 2-D is the most difficult part. If you do that properly all the work is done it seem to me. I don't really udnerstand how they do those images. I have one in a book I am using here --

(or maybe they sculpt the project out in the real world and then diagram the lines directly onto the sculpt and then photograph it and translate those images into 2D?)