Edit:
Ok,
actually I learned there are two "branches" of firmware for whatever reason. Here's an example for US Roadsters:
7839144 → 7839423 → 7840451
7839146 → 7839425 → 7840453 → 7841210
Not sure why, the first path versions always end in ZUHC and the second is ZWHE. They are both BT93 (US...