Austria should really be Österreich in the acronym if using native languages (DOCH), but the acronym is using the international vehicle codes so DACH it is (means "Roof" in German), it would be DEATCH if using ISO codes, which would be too close to Dutch or Deutsch.
Confoederatio Helvetica is the perfect neutral Latin term for Switzerland, and it's always known as CH by everyone. CN Germany is known as CN GAS (Germany, Austria, and Switzerland) internally, as someone who used to work for Turner part-time patroned the international threads on here years ago said it was, and it's also self-evident on the WBD website (see the URLs for press releases from that region "de-gas", and also the country switcher).
press.wbd.com
Hannes Heyelmann, already Warner Bros.' executive vp programming for Europe, the Middle East and Africa, will oversee production for German-language Europe, including theatrical titles and local-language originals for HBO Max.
www.hollywoodreporter.com
Regarding ad sales for Nordic, as far as I know, it has always been in-house:
https://www.linkedin.com/in/bofalkostergaard