Question

At which place in earth acceleration due to gravity is zero and why?

Answer 1

The only place where gravity is effectively zero is not on the Earth, but at the center of the Earth. At the Earth's center, all the mass is equally distributed, evenly in all directions, and so the net vector sum is zero. No one has been there and we can't even drill a hole anywhere near there.

Answer 2

At the centre of the earth.