Dial plan for zap channels

I have 2 FXO cards TDM2406B in on my asterisk,one im using for incoming calls channels 1-24 and 25-48 outgoing channels,i was using a2billing platform on this,im able to get incoming calls on all channels but at once only one call is routing out side from 2nd FXO card channels 25-48.Pls let me know whether outgoing dial plan mentioned below is correct or not,if not pls let me know appropriate dial plan with round robin ascending.

current dial plan :

exten =>_X,1,Dial(Zap/1/25,26,27,28,29,30,31,32)

Do i need to add one extension each for each country code,pls clarify.