FactorTermsList[(3 x^4)/(2 Sqrt[\[Pi]]) - (9 x^2 y^2)/(2 Sqrt[\[Pi]]) + (9 y^4)/( 16 Sqrt[\[Pi]]) - (9 x^2 z^2)/(2 Sqrt[\[Pi]]) + (9 y^2 z^2)/(8 Sqrt[\[Pi]]) + (9 z^4)/(16 Sqrt[\[Pi]]),{x,y,z}]