Split or trim brep by another brep

Hello everyone. I am very new user of grasshooper and this forum. I have do to something with STL file in rhino. I hope that you will help me. So, my problem is:
I have .stl file:
leg_scaled.stl (384.3 KB)
It is just human leg mesh.
Now i have to import it to rhino, copy it and move a little to get something like that:
The most important point of this work is to split this two breps and get the difference of this. I cant do it :confused:
here is my file, i was trying to do something with solid differences, but it doesnt work :confused:
forum_mcneel.gh (10.8 KB)

if you have a mesh, it seems better to stay on mesh. At the moment mesh tools from rhino are not always reliable to boolean meshes.
I used Dendro plugin to make the difference

You can also use a smoothing in order to have something better. Also you will have invalid meshes. So you will have to heal them. I used my plugin Nautilus but you’ll find on forum some little scripts to heal an invalid mesh.
As you have many meshes you must use Disjoin mesh and take the bigger.

You can also internalize geometry as I did in the gh file.
forum_mcneel_LD.gh (151.0 KB)