What happens with Zoo Tycoon and Windows Vista's compatibility changes?

The older series of Zoo Tycoon games aren't compatible with any themes you use on your Windows Vista computer (including the Windows Aero theme), other than the original theme, which came with the operating system (Windows Vista Basic for example).

Since the newer Zoo Tycoon 2 series of games are made by Games for Windows and are designed to work with Vista, they won't change what theme you use, and are fully compatible.