If one object is moving with constant velocity and the other object has zero acceleration, their relative velocity will be equal to the velocity of the object that is moving with constant velocity. This is because acceleration is the rate of change of velocity, and when an object has zero acceleration, its velocity remains constant.
So, if object A is moving with a constant velocity of vA, and object B has zero acceleration, the relative velocity of object B with respect to object A will also be vA.