I am new to ZTD, just read a couple of articles about it and out of curiosity did a Google search on the ZTD tools. To my surprise, there were none. Is it because there don't need to be ZTD-specific tools and GTD tools will cover that well or was I just bad at searching?
In case you're looking for web-based tools or are already into Remember the Milk, this ZTD workflow implementation might help you. I have been using it with a good experience so far.