In any case, keep in mind that the proceeding still remains valid even if Zeroshell is configured to act as a layer 3 router instead that as bridge. This is because the QoS classes are attached directly to the network interfaces (Ethernet, VPN, PPPoE, VPN bond and Bridge) and do not depend on the selected forwarding mode (routing or bridging).
Got a Netgear Router? Disable QoS | Tom's Guide Jul 26, 2018 How to Use Quality of Service (QoS) to Get Faster Internet Jul 03, 2017 Prioritize VPN Traffic by QoS | DrayTek Sep 20, 2018 Implement Quality of Service in Microsoft® Teams
VPN bandwidth presents a serious challenge when the VPN is connected over broadband Internet connections. Vendors tout the ability to provide bandwidth controls and QoS, but you must consider that the traffic will be in the same queue as any other Internet traffic.
[Adaptive QoS] Introduction of QoS | Official Support Jun 16, 2020
QoS Challenges with VPNs | The Packet University
Configure QoS on your Cisco router with this template Nov 16, 2006 Firewall Settings > QoS Mapping Site to Site VPN over QoS Capable Networks Site to Site VPN over Public Networks If the network path between the two end points is QoS aware, SonicOs can DSCP tag the inner encapsulate packet so that it is interpreted correctly at the other side of the tunnel, and it can also DSCP tag the outer ESP encapsulated packet so that its class can be How to set up Quality of Service (QoS) | DrayTek