CA warns that the bot has been revised to be more resistant to reverse engineering and more focused:

The latest Zeus bot configuration contains list of targeted financial institution from Spain, Germany, United Kingdom, and USA. The previous versions contains all the list of financial institutions from different countries around the world, while the new version only contains two targeted countries and currently paired as: Spain-Germany and UK-USA

One could guess that these targets are derived from the success of past bot versions. Attackers are evolving their product for better return margins.