Gerzbuehle is the name given to the "western" territory overseen by Viper Manor, once ruled by General Viper. It probably encompasses the area known as the Regionna outlands; Lynx is said to govern these lands. This possibly implies that Viper Manor lost control over all Gerzbuehle when General Viper was deposed. Gerzbuehle also probably contains the town of Regiorra and Staik Lake. It is presumably located in western Zenan.
utunnels has helped try and pinpoint things by retranslating the Japanese script. His comments: "西のゲルズブーレ means Gerzbuehle of the west, not west territory of Gerzbuehle. LOL I feel the translator sometimes messed with の too much. It is not always "of" in English. Similarly, "remote town Regiorra" is better, not to be confused with a remote town of Regiorra...it keeps saying the frontier Regionna/Regiorra in the Japanese script, which is sometimes omitted in the translated version.
- Regionna(if Regiorra is a typo) is a frontier/remote town/region (of what?).
- Lynx is the ruler of Regionna.
- Viper is the ruler of Gerzbuehle.
- Gerzbuehle is a western region/country/state/town, whatever.
- Whether Regionna and Gerzbuehle are part of a bigger kingdom, or whether one is part of another, it is not mentioned.
- Since Regionna is a remote/frontier region, it is politically less important. That's why Serge feels strange Porre would notice this place.
Possible locations of Gerzbuehle on the Chrono Trigger overworld, as postulated by GrayLensman.