A smooth transition between edges of tho parts of mesh I wish to know is there a way to make a smooth transition between edges.  For example, I have two different meshes and if I combine these meshes in single mesh, subsurf will ruin overall shape of the object. So, I need to combine these meshes somehow, but with smooth transition between edges. 
It must looks like this picture 


The only way i imagened is to create some kind of retopo. I mean, I create new object and use old objects as a base for Shrinkwrap modifier. May be there is a simplier solution? Two buttons in ZBrush, for example? Something like "mask sharp regions" and "make edges less sharp", or somethiing like that. Thank you :-)
Why don't you build it from scratch without any boolean, shrinkwrap, retopo, etc?