Unity - How to cut a sprite in half using the form of another sprite

So basicly what im trying to do is:

I have 2 sprites. One is the back sprite which will be cut in half and the other sprite is the front sprite which will be the form (look attached pictures). The original sprite should get split into 2 new Sprites/Meshes (each half forms a new one).

I already made something similar with cutting things with a straight line but i figured out that this is waaaay harder.

How can i start with this? I was trying and googling for a few hours now and couldnt really find something.