Question

How does blood return to the heart if the blood pressure in the veins is zero?

Answer 1

It doesn't, not that I know

Answer 2

Blood is returned to the heart by muscular massage. As your muscles move (especially leg muscles), the veins are squeezed to move the blood. Valves in the veins make sure the blood goes in the correct direction. This is why people who sit around all day have problems with blood pooling in their leg veins, resulting in varicose veins.

Courtesy of @proxszy

Answer 3

@Teddylover101