site-2-site vpn connect to the second address

Hi All,

I want to create a Site-2-Site VPN between Foritgate 51E and Zywall

The forigate WAN2 is used with subnet 255.255.255.248 for the VPN I want the Zywall to connect to the second address that is available so lets say I have 1.1.1.1/255.255.255.248 I want the VPN connect to the 1.1.1.3

Is this possible? I only can select the WAN2 in the VPN