Ask a volunteer to place a zip tie around your wrists. When he is putting the zip tie around your wrists, tighten your chest muscles to make your wrists occupy a greater space. When the volunteer is finished tightening the tie, you will have a little bit of slack.
Look around for a small shim such as a screwdriver, pin or nail file.
Insert the shim into the locking portion of the zip tie, using one of your hands, if there is enough slack. If there is not enough slack for your hands, hold the shim in your feet and wedge it into the locking mechanism.
Use the shim to lift the small latch in the locking mechanism that bites into the teeth of the zip tie. Widen your hands, while holding the latch up, to pull the zip tie through the locking mechanism.
Continue to widen your hands until the zip tie is completely removed.