Answer
$(x^2+y^2-z^2)(a+b+c)$.
Work Step by Step
The given expression is
$=ax^2+ay^2-az^2+bx^2+by^2-bz^2+cx^2+cy^2-cz^2$
Factor out the common terms.
$=a(x^2+y^2-z^2)+b(x^2+y^2-z^2)+c(x^2+y^2-z^2)$
Again factor out the common terms.
$=(x^2+y^2-z^2)(a+b+c)$.
