Two-firewall setup: Route from internal LAN to DMZ

[budspencer]

I'm setting up a dual firewall infrastructure as follows:

pfSense -> DMZ ->OPNSense -> internal LAN

The IP ranges and interfaces are as follows:
pfSense Server:
  - WAN interface: DHCP
  - DMZ interface: 10.22.0.1/24
  - Interface connecting this firewall with the internal: 10.23.0.1/24

OpnSense Server:
  - WAN interface: (disabled)
  - Interface to pfSense firewall: 10.23.0.2/24
  - Internal LAN interface: 10.24.0.1/24

The basic stuff like VPN and stuff within the internal LAN works. Now I'm struggling with setting up correct routes to access the DMZ from the internal LAN.

For example, I'm trying to ping server 10.22.0.2 in the DMZ from server 10.24.0.4 in the internal LAN. Obviously, it cannot be reached yet, because I need to somehow route to 10.22.0.0/24 via 10.23.0.1 (I guess).

How should I configure routing in this case? Or is something wrong with my network IPs?