Question: Does HiG have exclusivity with Klaus-Jürgen Wrede, and then others like ZMG or RGG have to work with HiG?
KJW has a deal with HiG for Carcassonne. Then HiG sells the rights to other publishers to release the game in their respective countries.
Or does ZMG have an independent arrangement with Wrede, separate from HiG? -
This seems not to be the case. He is the author of the game, although Bernd Brunnhofer helped him polish some rough edges and improve the original game.