Firewall - DMZ Design

Hello Guys,

I have to re-design a firewalled DMZ design. I have this idea in my head to working pretty standard based.

This means a front-end firewall cluster to connect towards the internet and the WAN. Behind this firewall cluster i would like the services cluster: F5 - Other

A Back-end firewall cluster that will connect the LAN and incoming management subnets towards the LAN.

The problem is that i'm still a bit junior on a security designs, so i would say that maybe incoming connections from the front-end cannot be allowed to the back-end firewalls without going through services cluster. Like a server in a LAN subnet that gets connected via the internet through an F5 cluster. (LTM)

Is there like a "golden" standard to follow? Or like a reference design? I know for dual connected ISP access there was a design on this reddit. I'm wondering if there is one for Firewalls as well.