/ip firewall mangle
add action=mark-connection chain=prerouting comment=ISP1 in-interface=ether1 new-connection-mark=From-ISP1 passthrough=yes
add action=mark-routing chain=prerouting connection-mark=From-ISP1 new-routing-mark=to-ISP1 passthrough=yes
add action=mark-routing chain=output connection-mark=From-ISP1 new-routing-mark=to-ISP1 passthrough=yes
add action=mark-routing chain=output new-routing-mark=to-ISP1 passthrough=yes src-address=10.10.10.10
add action=mark-connection chain=prerouting comment=ISP2 in-interface=ether2 new-connection-mark=From-ISP2 passthrough=yes
add action=mark-routing chain=prerouting connection-mark=From-ISP2 new-routing-mark=to-ISP2 passthrough=yes
add action=mark-routing chain=output connection-mark=From-ISP2 new-routing-mark=to-ISP2 passthrough=yes
add action=mark-routing chain=output new-routing-mark=to-ISP2 passthrough=yes src-address=20.20.20.20
add action=mark-routing chain=prerouting comment=LAN_0_ISP1 disabled=yes new-routing-mark=ISP1 passthrough=no src-address=192.168.0.0/24
add action=mark-routing chain=prerouting comment=LAN_1_ISP1 new-routing-mark=ISP1 passthrough=no src-address=192.168.1.0/24
add action=mark-routing chain=prerouting comment=LAN_0_ISP2 new-routing-mark=ISP2 passthrough=no src-address=192.168.0.0/24
add action=mark-routing chain=prerouting comment=LAN_1_ISP2 disabled=yes new-routing-mark=ISP2 passthrough=no src-address=192.168.1.0/24

/ip route rule
add src-address=10.10.10.10/32 table=ISP1
add src-address=20.20.20.20/32 table=ISP2
add dst-address=192.168.0.0/24 table=main
add dst-address=192.168.1.0/24 table=main
add routing-mark=to-ISP1 table=ISP1
add routing-mark=to-ISP2 table=ISP2

/ip route
add distance=2 gateway=10.10.10.10 routing-mark=ISP1
add distance=3 gateway=20.20.20.20 routing-mark=ISP2
add comment=WAN1 distance=2 gateway=10.10.10.10
add comment=WAN2 distance=3 gateway=20.20.20.20