Find the greatest common factor of the following monomials:

$3abc$ and $9xyz$

Find the greatest common factor of the following monomials:

$x^{2}y$ and $2xy$

Find the greatest common factor of the following monomials:

$2lmn$ and $4lpq$

Find the greatest common factor of the following monomials:

$he$ and $she$

Find the greatest common factor of the following monomials:

$6x^{2}yz$ and $15x^{2}y{z}^2$

Find the greatest common factor of the following monomials:

$-12l^2{m}^2$ and $108l^{3}m$

Find the greatest common factor of the following:

$4\left(b+c\right)$ and $8\left(b^2-c^2\right)$

Find the greatest common factor of the following:

$48ab\left(l+m\right)$ and $64a^2{b}^2\left(l^2-m^2\right)$

Find the greatest common factor of the following:

$ap+aq+bp+bq$ and $\left(p^2-q^2\right)$