A need to add a second route domain?

I have one public dmz range( a /24), which is full, so a second /24 range was added. The problem is due to the fact that these networks have different gateways on the firewall they are connected to, and therefore im running into async routing, and the connections are lost.

 

I have looked into auto last hop, but this is enabled, and got me nowhere.

 

So im wondering now if i should add a second route domain, where this new subnet resides. Which will give me two route domains:

 

0 - the original dmz range 1 - the newcly created dmz range

 

is there anything i should take into consideration when setting this up, and is it even possible to make it work like i hope it will?