This is just like Shomen Uchi Undo (which, by the way, you should learn first), except it's done in two direction. It's perfectly applicable to our modern day lives in which we have many competing demands for our attention. (Oops, excuse me for a minute, there's the phone.)

Double click the black & white picture above to play a video of Zengo Undo, single click to stop. If the mini-video didn't download automatically, you can get it while you're reading. It's only 90 K.
(Get the most recent Quicktime plug-in for best performance.)

• Turn on the balls of your feet. This will allow you to turn smoothly and quickly, without losing your balance. Experiment with turning on your heels. You'll find it's much harder to maintain your balance.
• Keep your head up and your eyes forward.
• Keep One-Point throughout. This will allow you to give your full attention first to the front, and then to the back. If you try to concentrate on too many things without keeping One-Point, you soon feel drained. By keeping One-Point, you can calmly focus on each new item that demands your attention.
• Here's something that applies to all ki exercises: Don't get hung up on always trying to keep One-Point and positive mind. Sometimes, you should just do the ki exercise and see what it teaches you. All of these exercises, when done with correct (or close to correct) form will naturally enhance your feeling of One-Point, relaxation, and overall mind/body coordination. So just enjoy the exercise.
• After each 180 degree turn, try taking a small step forward with your front foot to help propel your hips and arms forward.
• Have a friend test your stability. Do the exercise a few times. Then, after each 180 degree turn, have your friend try to upset your balance by gently pushing forward on the small of your back. Don't let him push too hard, though. The idea is to reinforce your feeling, not to frustrate you.
• Apply this exercise to daily life. When you have many things to do, keep One-Point and calmly give one item your full attention. The human mind isn't designed to focus on more than one thing at a time. Ever try to listen to one person on the phone, while another person in the room tried to talk to you, too? Your mind is split, and at best you can only alternate between catching a few of one person's words, and then a few of the other's.