Darreth,
When you setup your VCR, the Harmony will map common used functions to the hard keys, fast forward, stop, pause, play etc. It may use one of the hard buttons for the "smart cue", if this button is the same as FF. If not, you can add a "Change Button Function" to your Play a Video activity which overrides the default Hard-Button function with whatever you choose. Since the ZAP button has no functionality in this mode, this would be a prime candidate for re-definition.