K568 :
b^2*c^2*x^2*y - c^4*x^2*y + a^2*c^2*x*y^2 - c^4*x*y^2 - b^4*x^2*z +   b^2*c^2*x^2*z - 2*a^4*x*y*z + 2*a^2*b^2*x*y*z - 2*b^4*x*y*z +   2*a^2*c^2*x*y*z + 2*b^2*c^2*x*y*z - 2*c^4*x*y*z -   a^4*y^2*z + a^2*c^2*y^2*z + a^2*b^2*x*z^2 - b^4*x*z^2 - a^4*y*z^2 +   a^2*b^2*y*z^2 = 0