2 wan + 2 fire + 1 mdz

[ns007532 <ns007532@bragatel.pt>]

Hi

I recently upgrade my system with one more wan connection, connect to a 
new firewall(Debian + iptables + snort + portsentry and bind9, etc.). I 
only have one dmz box.
I have 2 nics (eth0 and eth1)on dmz 10.196.3.2 and 10.196.4.2, in the 
firewall1 10.196.3.1 and in firewall2 10.196.4.1.
The problem is the default gateway on eth0 on dmz 10.196.3.2 who is 
10.196.3.1, so a connection from wan2  62.123.x.x in firewall2 gets to 
dmz, but the response is from the gateway and go back as martian source 
to firewall1!

How can i resolve this?

Thanks in advance.