x^4+y^4+0.2*z^4-1.2*x^2*y^2+3.6*y^2*z^2+3.6*z^2*x^2+16*x^2*z-16*y^2*z-7.5*x^2-7.5*y^2-47.5*z^2+40*z+64.0625