One reason A ZPrinter® is fast is because it prints up to a half inch stripe at a time. This means that in almost any orientation you can print your parts fast. But if you understand part orientation you can maximize the speed and the quality of your build. In general the fast axis, or the direction the carriage moves in, is the fastest. The slow axis, or the direction the entire gantry moves in, is a bit slower. And, the Z axis is the slowest. In addition, the fast axis does not have to travel the full length of the gantry. So if you move your part to the edge of the build where the fast axis starts printing your part will print even faster. In other words, if the printer you are using has 10 inches of travel in the fast axis but your part is only 2 inches long, the carriage will only move as far as it has to in order to print the part. If you position the part in the center of the build area the carriage will have to travel 7 inches to start the fist stripe. For some parts the difference in print speed might not be noticeable but for a 2000 layer build the added time per layer accumulates and could be significant.
The main point is that by knowing how your printer works you can optimize your results and be more successful using your printer. A slight adjustment to your part orientation in the build area can result in significant improvements.