/ip firewall mangle
add chain=input in-interface=(interfacewan1) action=mark-connection new-connection-mark=(interfacewan1)_conn
add chain=input in-interface=(interfacewan2) action=mark-connection new-connection-mark=(interfacewan2)_conn
add chain=output connection-mark=(interfacewan1)_conn action=mark-routing new-routing-mark=to_(interfacewan1)
add chain=output connection-mark=(interfacewan2)_conn action=mark-routing new-routing-mark=to_(interfacewan2)
add chain=prerouting dst-address-type=!local in-interface=(interfacelan) per-connection-classifier=both-addresses-and-ports:2/0 action=mark-connection new-connection-mark=(interfacewan1)_conn passthrough=yes
add chain=prerouting dst-address-type=!local in-interface=(interfacelan) per-connection-classifier=both-addresses-and-ports:2/1 action=mark-connection new-connection-mark=(interfacewan2)_conn passthrough=yes
add chain=prerouting connection-mark=(interfacewan1)_conn in-interface=(interfacelan) action=mark-routing new-routing-mark=to_(interfacewan1)
add chain=prerouting connection-mark=(interfacewan2)_conn in-interface=(interfacelan) action=mark-routing new-routing-mark=to_(interfacewan2)
/ip route
add dst-address=0.0.0.0/0 gateway=(iprouterwan1) routing-mark=to_(interfacewan1) check-gateway=ping
add dst-address=0.0.0.0/0 gateway=(iprouterwan2) routing-mark=to_(interfacewan2) check-gateway=ping
add dst-address=0.0.0.0/0 gateway=(iprouterwan1) distance=1 check-gateway=ping
add dst-address=0.0.0.0/0 gateway=(iprouterwan2) distance=2 check-gateway=ping