Holfung-Borzoi, or more colloquially, Holzoi, is the principality where Zulenna Luzhakna's family rules. At some point in the past two or three decades, the Heterodyne Boys , which subsequently allowed them to resist Baron Klaus Wulfenbach's ongoing Europan pacification efforts to the point of negotiation rather than outright conquest.
The name of its capital is Mozenplatz.
Immediately north of Holfung-Borzoi might be the Duchy of Holstein. It is also adjacent to the Grand Duchy of Orcznik. The principality itself seems to be the equivalent of, neighbor to or incorporate the Grand Duchy (Duchies) of Mecklenburg.
Following the Time-skip, Baron Gil an intelligence report that the principality and its feuding neighbor the Grand Duchy of Orcznik have agreed to a "peace treaty" arranged by the Queen of the Dawn, AKA Zola, which in reality most likely means that the population have all been infected with Slaver Wasps.
Another post-Timeskip development is discussed on the Twitter account of Othar Tryggvassen (Gentleman Adventurer), in which Othar to investigate the principality and its "famous cherry cream waffles" in person. Eotain the Geister ends up tagging along with him. Upon arriving on the scene, they learn from the Corbettite Monks that The Other is indeed openly wasping anyone who visits the principality, though the Corbettites were somehow able to fight off this attack, even as they continue to run their supply trains into the area to supply a resistance movement led by an individual called "The Steel Shrike".
Possibly relevant outside information
You will not find Holfung-Borzoi on maps in our world. You will find breed standards for Borzoi among the documents used by kennel clubs. Borzoi is Russian meaning "Quick Dog" — Borzoi are sighthounds, chasing their prey by detecting motion rather than scent, and the term is used in Russia for a group of breeds, but in English-speaking countries as a synonym for the Russian Wolfhound.
Well, actually, there is a geographical Borzoi, in Chechnya, population four thousand or so.
Holfung is a placename with a sort of Nordic-Teutonic sound to it and no equivalent as a geographical term in our timeline, but it appears to be a scientific term in German, a Turkish business term, and a surname in Chinese (and possibly other languages).