Route IPv6 through another interface? OVH

[harmonyp]

I am using OVH vRACK on vmbr1

iface vmbr0 inet6 static
    address 2001:41d0:803:8400::1/128
    gateway fe80::1
    up ip -6 route add 2001:41d0:803:8400::/56 dev vmbr0


auto vmbr1
iface vmbr1 inet static
    address 192.168.0.122/16
    bridge-ports bond1
    bridge-stp off
    bridge-fd 0

routing the IPv6 block directly in the vmbr1 section won't work as it's the OVH vRACK. How can I route this IPv6 block (2001:41d0:803:8400::/56) into the vmbr1 adapter through vmbr0 first.