Multiply the following.

$\left(x^2+y^2+z^2\right)(x+y+z)$

Multiply the following.

$(a+b-c)(a-b+c)$

Multiply the following.

$\left(3x^2+xy-2\right)\left(x+2y^2+xy\right)$

Multiply the following.

$(5a+3b)\left(a^2-b^2\right)$

Multiply the following.

$(-5m-3n)(-2m+3n)$

Multiply the following.

$(m-n+p)(m+n-p)$

Multiply the following.

$\left(2a^2-2ab+2b^2\right)\left(\frac{a}{2}-\frac{b}{2}\right)$

Multiply the following.

$(5xy-x+2 y)(x+y-x y)$

Simplify the following expressions.

$p(p-q)+q(q-p)$