lambda calculus – Beta reduction of $SS(SK)$

I want to $beta$ reduce the expression $SS(SK)$, where

$S = (lambda x y z. z (y x)) y x z$

$K = lambda x y.x$

I have found out that the expression $S$ can be $beta$ – reduced to $z (x y)$

I don’t want to just replace the actual $S$ expression in the $SS(SK)$ as it would be huge, so I would like to know if I can directly introduce the beta reduction of $S$ within the expression $SS(SK)$