ECMP settings for Outgoing packets uses same routing decision

Hello,

at wiki page for Outgoing packets uses same routing decision there are few mangle rules as below;

/ ip firewall mangle
add chain=input in-interface=wlan1 action=mark-connection new-connection-mark=wlan1_conn
add chain=input in-interface=wlan2 action=mark-connection new-connection-mark=wlan2_conn
add chain=output connection-mark=wlan1_conn action=mark-routing new-routing-mark=to_wlan1     
add chain=output connection-mark=wlan2_conn action=mark-routing new-routing-mark=to_wlan2     
/ ip route
add dst-address=0.0.0.0/0 gateway=10.111.0.1 routing-mark=to_wlan1 
add dst-address=0.0.0.0/0 gateway=10.112.0.1 routing-mark=to_wlan2

I set these rules, but rules for router it self, if I want to do mangle rules for forwarded traffic what should i do ?

Thanks for help

in chain=prerouting

thanks sebastia,
do I need mark mark-connection ?

For routing management only routing-mark is needed.