K521 :
a^6*x^2*y - 3*a^4*b^2*x^2*y + 3*a^2*b^4*x^2*y - b^6*x^2*y - a^4*c^2*x^2*y +   8*a^3*b*c^2*x^2*y - 2*a^2*b^2*c^2*x^2*y - 8*a*b^3*c^2*x^2*y +   3*b^4*c^2*x^2*y + 16*a*b^2*c^3*x^2*y - a^2*c^4*x^2*y -   8*a*b*c^4*x^2*y - 3*b^2*c^4*x^2*y + c^6*x^2*y + a^6*x*y^2 -   3*a^4*b^2*x*y^2 + 3*a^2*b^4*x*y^2 - b^6*x*y^2 - 3*a^4*c^2*x*y^2 +   8*a^3*b*c^2*x*y^2 + 2*a^2*b^2*c^2*x*y^2 - 8*a*b^3*c^2*x*y^2 +   b^4*c^2*x*y^2 - 16*a^2*b*c^3*x*y^2 + 3*a^2*c^4*x*y^2 + 8*a*b*c^4*x*y^2 +   b^2*c^4*x*y^2 - c^6*x*y^2 - a^6*x^2*z + a^4*b^2*x^2*z + a^2*b^4*x^2*z -   b^6*x^2*z - 8*a^3*b^2*c*x^2*z +   8*a*b^4*c*x^2*z + 3*a^4*c^2*x^2*z + 2*a^2*b^2*c^2*x^2*z -   16*a*b^3*c^2*x^2*z + 3*b^4*c^2*x^2*z + 8*a*b^2*c^3*x^2*z -   3*a^2*c^4*x^2*z - 3*b^2*c^4*x^2*z + c^6*x^2*z + a^6*y^2*z -   a^4*b^2*y^2*z - a^2*b^4*y^2*z + b^6*y^2*z - 8*a^4*b*c*y^2*z +   8*a^2*b^3*c*y^2*z - 3*a^4*c^2*y^2*z + 16*a^3*b*c^2*y^2*z -   2*a^2*b^2*c^2*y^2*z - 3*b^4*c^2*y^2*z - 8*a^2*b*c^3*y^2*z +   3*a^2*c^4*y^2*z + 3*b^2*c^4*y^2*z - c^6*y^2*z - a^6*x*z^2 +   3*a^4*b^2*x*z^2 - 3*a^2*b^4*x*z^2 + b^6*x*z^2 - 8*a^3*b^2*c*x*z^2 +   16*a^2*b^3*c*x*z^2 - 8*a*b^4*c*x*z^2 + 3*a^4*c^2*x*z^2 -   2*a^2*b^2*c^2*x*z^2 - b^4*c^2*x*z^2 + 8*a*b^2*c^3*x*z^2 -   3*a^2*c^4*x*z^2 - b^2*c^4*x*z^2 + c^6*x*z^2 - a^6*y*z^2 + 3*a^4*b^2*y*z^2 -   3*a^2*b^4*y*z^2 + b^6*y*z^2 + 8*a^4*b*c*y*z^2 -   16*a^3*b^2*c*y*z^2 + 8*a^2*b^3*c*y*z^2 + a^4*c^2*y*z^2 +   2*a^2*b^2*c^2*y*z^2 - 3*b^4*c^2*y*z^2 - 8*a^2*b*c^3*y*z^2 + a^2*c^4*y*z^2 +   3*b^2*c^4*y*z^2 - c^6*y*z^2 = 0