Work is being done by a force when it displaces the object in the direction of the force. Work done is the same while climbing a mountain on a zigzag path and for one straight up the side as net displacement is the same. but it is easier to climb on the zigzag path because work is done along a longer path and gravitational pull is less at any instant as compared to one straight up. The distance is shortest when climbing the straight path thus gravitational force experience is more and it is difficult to climb.
