Hi tahsin1982,

Well you can lay out the uvs with zbrush but I prefer to lay them out with a separate app called headus. I then tweak the uvs to get them exactly right but headus helps speed the whole process up greatly.
Zbrush does not rely on uvs as instead of painting onto a uv'd model you are polypainting. Because of this you have to subdivide your mesh a about 6-7 times in order to be able to get the details in your texture map. You can then either layout the uvs in zbrush or export the model at its lowest level to do the uvs elsewhere. When you then re-import the uv'd mesh into zbrush the new uv's will be transferred to your model allowing you to export the texture map. Mudbox is better in my opinion with regards to high res texturing though as you are not held back by the polypaint option and can paint a high res texture onto a low res model.
With regards to having a high res mesh when you go back into maya there are a number of ways to solve this.
1st of you want to make sure the mesh you rig has a good amount of poly's to work with. If you have a mega low base mesh you will probably want to be working with the sculpt you create in mudbox at 1 subdivision for the rigging.
In order to use all of the details you will be sculpting such as scales etc there are a few options.
You could export the high res sculpt and set it up as a wrap deformer so it is driven by the low res mesh. This would probably not be the best method though as you will have a lot of geometry and it will make maya very unstable.
The other option is to export either a normal or displacement map. If you have not heard of these they are textures which you can plug into your shaders in Maya. I personally prefer to work with normal maps, they are simply plugged into your bump node on your shader. You will need to set it up as tangent space normals though.
Displacement maps achieve more detail but the render times can be very excessive with Maya and mental ray. I know others such as vray and renderman can chuck out the renders much faster but I found mental ray to suck at calculating them. That said it was a long time ago I last used them with mental ray so it may be a lot faster now.

Hope this info helps you on your way and best of luck.