RB750GL as FIREWALL (FILTERING)

Hi, i need to setup RB750GL only as FIREWALL(FILTERING) for hotspot network.

I have a Zyxel Hotspot Hardware but there is no firewall in it. Zyxel hotspot work as DHCP server.
I need to setup this scheme: Zyxel (HotSPot+DHCP+DNS, 192.168.3.) —> RB750GL (FIREWALL, FILTERING, DHCP+DNS addresses PassThrough from HotSPot to clients(bridging)) —> Clients (192.168.3.).
And i want some IP addresses (like 192.168.3.7-9) to PassThrough RB750GL (FIREWALL, FILTERING) in this config.

Maybe, there is ready example? Please, help!