Yes, I can see in the manual where the X0 and X1 ports are configurable as LAN or WAN. Our pro 2040 can do this. I didn't realize the TZ's also now support this.
If both ports are configured correctly, then I don't understand what you are trying to do. You can load balance outbound connections, but you can't determine where your inbound traffic will come from.
Perhaps if you explain what you are trying to accomplish we can better help you.