Solution: This is common because VPN clients modify network adapters. Click "More info" → "Run anyway." The official Zyxel client is digitally signed by "Zyxel Communications Corp."
The client is designed primarily for Windows environments. zyxel ipsec vpn client download link
If you are connected to the LAN side of a Zyxel USG/ATP firewall: Solution: This is common because VPN clients modify
If you need to establish a secure, encrypted connection to a Zyxel firewall (such as the USG, ATP, or VPN series) from a remote computer, the Zyxel IPsec VPN Client (formerly known as the ZyWALL IPsec VPN Client) is the proprietary software required for legacy IPsec connections. If you are connected to the LAN side
Below you will find the official download source, system requirements, and important notes regarding the software license.