Displacement can be zero as we can assume a body travels a circular path and end up where it started so in this case the displacement is zero.
Adding on to the previous answer.
Displacement can be zero when an object travels eg. 1 metre to the left and then 1 metre to the right.
The object ends up back at its original position.
For a vector question, assume a direction to be positive and another to be negative.
In this scenario, I will take right as positive, and left as negative.
The object travels