SSL VPN to Host in WAN Zone

Hi everyone. I'm having difficulties setting up the following:

 

SSL VPN to my LAN -> everything fine. Now theres a host in  the Zone between the XG and the Router/Modem which i sometimes want to connect to (it's a tiny web server). Here's a picture i draw of the situation:

The green arrow from my VPN Client (just a windows laptop with SSL (Open) VPN) is working, but no matter what i tried i can't get the red arrow to work.