Is it possible for the electric potential at the center of the cube to be zero?

Answer 1

Electric potential is a scalar which means you merely add up all the potentials at the center of the cube while ignoring the direction it is pointed in. I supposed voltage (or electric potential) could be 0 if you have an even number of positive and negative charges all with the same distance from the center (if the charges are on the corners of the square the distances would in fact be the same).

Answer 2

Yes, it is possible for the electric potential at the center of a cube to be zero if there is an arrangement of charges that cancels each other's effects such that the net potential at that point is zero. This would require a specific distribution of charges within or around the cube.