Sculpting Head splitting and sculpting in Zbrush

Turn on Live Boolean, append a shape (I used a cube for splitting the headcap, a sphere for the main head cavity, and several small cylinders for neck hole, magnet spaces, and that little notch for the s-hook), click on the button on the shape to subtract, fuss with shape as needed. Click on Line Fill PolyF to see the subtracting shape if you have lost track of where it is.



When you're happy with how it is, go to Boolean in the subtool menu and make Boolean Mesh.

And for the headcap, switch the shape use used to cut the headcap to intersection instead of subtraction.