2 wan and 2 lan cross failover

RouterOS Beginner Basics
1

hello

I have 2 WAN GW
say
W1 172.16.30.1 (eth1)
W2 172.16.30.2 (eth2)
and 2 lan
LAN1 192.168.0.0/24 (eth3)
LAN2 192.168.1.0/24 (eth4)

so, I need that LAN1 devices were on W1 internet, but faiolver on W2
LAN2 devices use the W2 internet but failover with W1,

So, inc ase of any wan failure both lan will use alive gateway,

Can I do it through routes only without marking?


or any tutorial on marking?

thanks