/ip firewall mangle add chain=prerouting in-interface=vlan1,vla
n2 action=mark-routing new-routing-mark=2
/ip firewall mangle add chain=prerouting in-interface=vlan3,vla
n4 action=mark-routing new-routing-mark=3
/ip route add routing-mark=2 gateway=wan2
/ip route add routing-mark=3 gateway=wan3