I would suggest to remove the internet router and let ZS do the job. If it is an adsl line set the modem to bridge mode (rfc1453) and setup ZS to PPPoE. Otherwise it is going to be a big mess with double NAT and port forward.
u can use the modem u already have, u simply set eth00 to b ur local network, then setup an internet connection, i am used to adsl so in my setup –> network i have eth00, eth01,ppp0 eth01 is linked to ppp0. ZS will do all your DHCP w/ minor setup, routing, firewalling.the NAT will work “out of the box” under adsl the NAT auto sets itself.
so if ur adsl comes in on eth00 and ur LAN is connected to eth01, set eth00 to the ip subnet that the router wants to use, set ur eth01 to ur LAN subnet, then under NAT enable it on eth00 and u should have connectivity. u may need to set a static route to the modem.
i have a router behind my main to separate a small problem subnet and i had to static route from them to the main gateway. the gateway is 192.168.0.1, their network is 192.168.1.0 so i set
Destination Netmask Type Metric Gateway Interface
0.0.0.0 0.0.0.0 Net 1 192.168.0.1 Up
As there are visitors of many nationalities on here, can I suggest that you do not use shortened versions of English words (‘u’ and ‘ur’ etc). It will make reading a lot easier for all concerned.