Z-fire can be usefull for locating units that already fire on you.
As for example units on fired me, i want to find them,then I z-fire on on the general location, and voila! they changed status thus discloseing thier loctaion.
But expending every round radicaly,is IMO just to supression,in turn,is rather gamish
Most HU opponents i've played don't like it.. and keep in mind the AI never ever z-fires.