Help with RancherOS network bridge

Hi, im wondering if anyone can help with cloud-config settings for a network bridge.
I have a simple eth0 interface (see bellow) plus a zerotier interface zt0 and I need to create a layer 2 bridge between them

        dhcp: true

the zerotier documentation describes making changes to /etc/network/interfaces

# The loopback network interface
auto lo
iface lo inet loopback

# The primary network interface you use for the basic connectivity of the server
auto eth0
iface eth0 inet dhcp

# the interface you use purely as a bridge (consider it a switch port); it does not get an IP address. 
auto eth1
iface eth1 inet manual

auto br0
iface br0 inet manual
    bridge_ports eth1 zt0
    bridge_fd 0
    bridge_maxage 0

however I’m not sure how to apply the same configuration via my cloud-config.yaml file.
thanks in advance for any help :smile: