LHS=−8abc+2(b+c)(c+a)(a+b)+2a(b+c)2+2b(c+a)2+2c(a+b)2
=2(b+c)(c+a)(a+b)+2a(b+c)2−8abc+2b(c2+2ca+a2)+2c(a2+2ab+b2)
=2(b+c)(c+a)(a+b)+2a(b+c)2+2bc2+2ba2+2ca2+2cb2
=2(b+c)(c+a)(a+b)+2a(b+c)2+2a2(b+c)+2bc(b+c)
=2(b+c)(c+a)(a+b)+2(b+c){a(b+c)+a2+2bc}
=2(b+c)(c+a)(a+b)+2(b+c)(c+a)(a+b)
=4(b+c)(c+a)(a+b)=RHS