You will have to do the following:
Internet – Servers
123.xxx.yyy.122 (Public IP 1) – Server 1
123.xxx.yyy.123 (Public IP 2) – Server 2
Internet – Static IP (Red) [IPCOP]
….[IPCOP] (Green) 192.168.0.1/24 – Switch – LAN Computers
….[IPCOP] (Orange) 192.168.1.1/24 – Switch – DMZ Computers
Public IPs:
123.xxx.yyy.121 (Public IP 3) – Default IP
123.xxx.yyy.122 (Public IP 1) – Alias 1
123.xxx.yyy.123 (Public IP 2) – Alias 2
Servers:
192.168.1.11 – Server 1
192.168.1.12 – Server 2
Port Forwarding:
123.xxx.yyy.122 (Public IP 1) – 192.168.1.11
123.xxx.yyy.123 (Public IP 2) – 192.168.1.12
SNATGui (Outbound)
192.168.1.11 – 123.xxx.yyy.122 (Public IP 1) [World sees traffic from server1 as IP address 123.xxx.yyy.122 (Public IP 1)]
192.168.1.12 – 123.xxx.yyy.123 (Public IP 2) [World sees traffic from server2 as IP address 123.xxx.yyy.123 (Public IP 2)]
World sees traffic from other computers behind IPCOP as IP address 123.xxx.yyy.121 (Public IP 3)