Deep Paint 3D is a completely different program from ZB and they do totally different things, furthermore they compliment each other and I use them together all the time.
For example, you would never compose or render a picture in DP3D, DP is strictly a texturing tool, after you have done your texturing you would take it back out to a 3D program for rendering. DP’s tight integration with Photoshop makes it a very powerful tool for doing realitic and accurate texturing. While ZB is more of an all-in-one solution, where you can experiment in real time with speculaity, reflectivity and so on. What I do is use Zbrush to make a great repeatable texture, then I bring it into Deep Paint and paint it onto the 3D model in the areas I want it.
Again they do many things that the other does not. DP is more of a tool to compliment and simplify the texturing tools of an existing 3D program, while Zbrush can be used independant of any 3D programs because it has advanced modeling/rendering functions built in.
Lobo