Matlab: Implement filter with no denominator
It's an odd notation but simple enough: $z^4% simeply means "shift the signal 4 samples to the left". That means its non-causal and can't therefore be implemented directly in a physical system. 

In practice, the workaround that works most of the time is to add overall "causality delay" to the system until everything is causal again. Whether this is applicable here or not, depends on the specifics of your application.