router 1 : AP bridge (wlan-1) for distribution to customer as access point
router 1 : AP station (wlan-2) for backbone to router-2
router 2 : AP bridge (wlan-1) for backbone to router-1
router-2 : AP bridge (wlan-2) for distribution to customer as Access Point
router-2 : ethernet to internet backbone
In such case use WDS between them, but to take this working properly use WDS-slave or WDS-Station instead of Station operation concerning bridging mode. But is your network is routed then use Station mode.
Ethernet over IP (EOIP) is better when is physical connection. and if you want to joint Router-1 and router-2 via wireless you have to use what I just said.