(a^2+9)^2(a-1)+36a^2(1-a)
=(a^2+9)^2(a-1)-36a^2(a-1)
=[(a^2+9)^2-36a^2](a-1)
=(a^2+9+6a)(a^2+9-6a)(a-1)
=(a+3)^2(a-3)^2(a-1)