Your Main.PRG. shall start with the following line...
=myInstance("A name for your Application")
Then just copy the following code and add it at the end of your main.prg.
******************************************
PROCEDURE myInstance
PARAMETERS myApp
=ddesetoption("SAFETY",.F.)
ichannel = DDEINITIATE(myapp,"ZOOM")
IF ichannel =>0
=DDETERMINATE(ichannel)
QUIT
ENDIF
=DDESETSERVICE(myapp,"define")
=DDESETSERVICE(myapp,"execute")
=DDESETTOPIC(myapp,"","ddezoom")
RETURN
******************************************
PROCEDURE ddezoom
PARAMETER ichannel,saction,sitem,sdata,sformat,istatus
ZOOM WINDOW SCREEN NORM
RETURN
**********************************************************
** EOF