Yes there is, but the fact that you're asking the question means that you need to learn a LOT more about JSF. Welcome to the JavaRanch, by the way!
A JSF action processor doesn't return a display string, it returns a dispatching directive. This directive - which is often a simple word like "success", "failure", or "not authorized" is used as a key into the navigations rules in the jsf config file to determine what view will be displayed when the action returns to the client. If there is no match, the previous view is displayed.
To return a value, make that value a property in a backing bean (typically the same bean that defines the action processor method). Then supply standard JavaBean setter/getter methods for it. You can then reference the returned value as a backing bean property in your displayed view. For example:
I recommend NOT capitalizing bean ID names, by the way. Leave that for classnames.
Note that although I used the same name (rez) as you did in your sample code, it's not the same "rez". That one would have gone out of scope when the method returned. That's why you need a "private String rez;" property in your backing bean.
An IDE is no substitute for an Intelligent Developer.