Hi Rafael,
AFAIK (and please correct me if I’m wrong) considering the setup you describe, the communication is only happening from server 3 (DMZ) to the other LAN application exposing the webservice. So if there is a firewall between the DMZ and this other LAN (which I assume there is), I’d look into the firewall rules.
Even though the module in the DMZ has a module from the Intranet Zone as a dependency, this Intranet module will be published as a library together with the module in the DMZ. The chapter ‘Understanding how the platform deploys eSpaces’ in this article explains this part with examples. Therefore the communication is only happening from the DMZ server to the other LAN exposing the webservice.
Furthermore, regarding the Deployment Zone Address, this is only available in OutSystems 11, so since you are on OutSystems 10 you should ignore this part.
Regards,
Nordin