Access remote VLAN over IPsec VPN using Zyxel routers

[...] but when tunnel is enabled i lost my internet connection and i can't ping devices on my LAN1

The issue with lost internet connection sounds pretty much like a "Split Tunnel" issue. If you didn't enable Split Tunnel in your VPN configuration, all traffic originating from your VPN client will go through your VPN gateway.

When enabling Split Tunnel, your VPN client will receive specific routes and therefore will only send interesting traffic in the VPN tunnel.

As for the other issue (unable to ping devices on LAN1), there are three things that can happen.

1. If you are trying to ping with the devices name, you obviously need your VPN configuration to "send" a DNS server to the VPN client that will resolve names on the LAN1 network. You can check if that's the issue by pinging the devices using their IPs. If it works, it's a DNS issue.

2. Some firewall rules might be missing. You might have to explicitly tell the firewall to allow traffic from and to the VPN clients. This should be verified by looking at traffic logs on the firewall.

3. Some routes might be missing. You didn't mention what IP your VPN client gets, but you have to make sure that the client knows how to route to the LAN1 network. You obviously also need to make sure that devices on LAN1 knows how to route whatever subnet you are using on the VPN client side. This can be verified by checking the routing tables on both devices in LAN1 and on your VPN client once it's connected to the VPN tunnel is up.

In ZyXEL switches, when you create the VLANs and give ports access to those VLANs it doesn't automatically assign those ports to the VLANs. I had to find another page to assign the ports to the correct VLANs.