\(2a^2b +4ab^2-a^2c +ac^2-4b^2c +2bc^2-4abc\)
\(=\left(2a^2b+4ab^2-2abc-4b^2c\right)-\left(a^2c+2abc-ac^2-2bc^2\right)\)
\(=2b\left(a^2-ac+2ab-2bc\right)-c\left(a^2-ac+2ab-2bc\right)\)
\(=\left(a^2-ac+2ab-2bc\right)\left(2b-c\right)\)
\(=\left[a\left(a-c\right)+2b\left(a-c\right)\right]\left(2b-c\right)\)
\(=\left(a+2b\right)\left(a-c\right)\left(2b-c\right)\)