a2b2(a-b)+b2c2(b-c)+c2a2(c-a)
=a3b2-a2b3+b2c2(b-c)+c3a2-a3c2
=(a3b2-a3c2)-(a2b3-c3a2)+b2c2(b-c)
=a3(b2-c2)-a2(b3-c3)+b2c2(b-c)
=a3(b-c)(b+c)-a2(b-c)(b2+bc+c2)+b2c2(b-c)
=(b-c)[a3(b+c)-a2(b2+bc+c2)+b2c2]
=(b-c)[a3b+a3c-a2b2-a2bc-a2c2+b2c2]
=(b-c)[(a3b-a2b2)-(a2c2-b2c2)+(a3c-a2bc)]
=(b-c)[a2b(a-b)-c2(a2-b2)+a2c(a-b)]
=(b-c)[a2b(a-b)-c2(a-b)(a+b)+a2c(a-b)]
=(b-c)(a-b)[a2b-c2(a+b)+a2c]
=(b-c)(a-b)[a2b-c2a-c2b+a2c]
=(b-c)(a-b)[(a2b-c2b)+(a2c-c2a)]
=(b-c)(a-b)[b(a2-c2)+ac(a-c)]
=(b-c)(a-b)[b(a-c)(a+c)+ac(a-c)]
=(b-c)(a-b)(a-c)[b(a+c)+ac]
=(b-c)(a-c)(a-c)(ab+bc+ac)