Squish problem

For some reason, I try to use the squish to flatten the 3D-STL(double curvature), but the result is so bad (see the following figure), does anyone help me how to solve it? (I do not divide the original 3-d STL, I must maintein the original 3D-stl).

Can you post the 3dm? I’m wondering if using the UVeditor would produce a more usable result depending on your goal.