To factor $ axy+bcxy-az-bcz $ we can use factoring by grouping.
Group $ \color{blue}{ axy }$ with $ \color{blue}{ bcxy }$ and $ \color{red}{ -az }$ with $ \color{red}{ -bcz }$ then factor each group.
$$ \begin{aligned} axy+bcxy-az-bcz &= ( \color{blue}{ axy+bcxy } ) + ( \color{red}{ -az-bcz }) = \\ &= \color{blue}{ xy( a+bc )} \color{red}{ -z( a+bc ) } = \\ &= (xy-z)(a+bc) \end{aligned} $$