This is the zig-zag shape we associate with lightening in drawings and it is the key to powerful reaction on the tennis court. Watch the best returners in tennis get ready and they are low, usually shifting their weight from side to side to prepare their core muscles to engage and produce a winning return. They continue to keep this wide stance going throughout the point as you recover from shots and prepare to move again. The lower center of gravity will create amazing, explosive movement and an intense feeling of balance. If done consistently, you will see improvement in the pace and depth of your shots with less effort from your arms and shoulders because you are now engaging the larger core muscles to hit the ball from the ground up.
Good luck, and remember: look like lightening, play like thunder!