Z brush can petty much do it all now both organic and hard surface. What is making the big programs loose ground against Z brush is it ability to do things so much faster then say in maya.
Example in Z brush i can create, UV map, texture, and make displacement maps 1000 times faster. Back in maya you have to layout the uv's and hand paint a flat map which in it self took so much time.
The big programs are great for animation,and FX but as far as modeling they are really falling behind now.
I am enough of an artist to draw freely upon my imagination, knowledge is limited, imagination encircles the world. (Albert Einstein)
https://www.artstation.com/kurtb