Hello BobC1958,
I understand that your hands are accidentally making the gesture to zoom in on your Surface Pro 3. I'll do what I can to help you with this.
I've gone through the settings and cannot find a way to turn this off. You could disable the touchpad altogether in pc settings and use a mouse. It may not be the solution you are looking for, but it would work as a workaround.
Let us know if that works or if you have any other questions.
Best Wishes,
Zack_T