(4b^2+ 2a^2- 4ab)(3ab+2a^2-3b^2) = 12ab^3 + 6a^3b - 12a^2b^2 + 8a^2b^2+4a^4-8a^3b-12b^4+12ab^3 = 4a^4 - 12b^4 - 10a^2b^2 - 2a^3b +12ab^3
(4b^2+ 2a^2- 4ab)(3ab+2a^2-3b^2) = 12ab^3 + 6a^3b - 12a^2b^2 + 8a^2b^2+4a^4-8a^3b-12b^4+12ab^3 = 4a^4 - 12b^4 - 10a^2b^2 - 2a^3b +12ab^3