Currently we do not have support for other VPNs to run alongside Guardian Firewall.
Guardian Firewall is developed and designed to work with Guardian VPN only at this time.
The way iOS is developed and the nature of using a VPN will only allow one VPN to work at a time to ensure your traffic flows through one secure tunnel and is not confused by attempting to run two VPNs simultaneously.
You may have multiple VPN clients installed on your mobile device but only one enabled or connected at a time. You may toggle on or off different VPNs per your personal preference. Please note when using other VPNs, the Firewall will no longer be detecting or blocking the traffic on your device.