Firewall Problem - Iptables bash multiple nic's

Hello I have written a simple firewall but have 4 nic's
Because i'm rather lazy i would like to write as little code as possible.

Is there a for loop i could use or some sort of array assignment to avoid writing a lot of
avoidable script lines?

My firewall script is accessible via pastbin:

"pastebin""/"baxzVuyH

kind regards,

Peter Harmsen