Hi Yayayi,
You need to refer FPM event id of the corresponding button but not action id. As you said you have given FPM_EVENT_ID as ZACT, write the code in process event of component controller of your WDP component in which IF_FPM_UI_BUILDING_BLOCK interface has been re-implemented.
But dont forget to follow the below steps shown in snapshot.
Hope this helps you.
Thanks
KH