mDNS uses a link-local multicast address (184.108.40.206) that cannot be sent off-link, so you cannot route mDNS packets.
4. Local Network
Control Block (224.0.0/24)
Addresses in the Local Network Control Block are used for protocol
control traffic that is not forwarded off link. Examples of this
type of use include OSPFIGP All Routers (220.127.116.11) [...