Mouse wheel zoom in zoom out issue

Question

Here while performing mouse wheel action the object in moving back and forth while moving the mouse wheel in or out. And also I want to know the purpose of the formula

            point.x = point.x * 2 - 1;
            point.y = -point.y * 2 + 1;

Here I have attached the function of the code where you can find the error which I have done in the calculation where zoom in or zoom out are happening in back and forth but not in healthy manner

 private actionMouseWheel = (): Function => {
        const that = this;
        const cameraManager = that._cameraHandler;
        const zoomStart = new Vector2(0, 0); //center of the position
        const zoomEnd = new Vector2(0, 0); //center of the position
        const zoomSpeed = 1.015; //speed of mouse wheel
        const zoomFactor = 2.015;
        let w;
        let xy = new Vector2();
        let dist = 0;
        let detail = {};
        let closestPoint = new Vector3();
        closestPoint = cameraManager.Target;

        const dispatchEvent = () => {
            that._orbitController.trigger('zoom', {
                type: 'zoom',
                detail: detail
            });
        };

        const interval = 15;
        let marker = true,
            counter1 = 0,
            counter2;
        function wheelStart() {
            marker = false;
            that._layerHandler.isFrustumCulled = true;
            dispatchEvent();
            wheelAct();
        }
        function wheelAct() {
            counter2 = counter1;
        }
        function wheelEnd() {
            marker = true,
                counter1 = 0,
                counter2 = 0;
            that._layerHandler.isFrustumCulled = false;
            that.render();
        }
        let pPoint = null;
        const callback = (resp) => {
            objCallback(xy, resp);
        };
        const objCallback = (point, id) => {
            point.x = point.x * 2 - 1;
            point.y = -point.y * 2 + 1;
            pPoint = null;

            const obj = that._pickingHandler.getPickingDataById(id);
            if (obj) {
                pPoint = that.updatePivotOrbitPoint(point, obj);
            }
            update(point);
            console.log("point on mouse wheel");
            console.log(point);
        };
        const update = (point) => {
            const dd = 1000; // 3048 * 0.5; // 3048mm = 10ft
            const ddd = 1000;
            if (pPoint !== null) {
                closestPoint = pPoint;
                dist = cameraManager.Eye.distanceTo(pPoint);
            }
            else {
                dist = cameraManager.Eye.distanceTo(closestPoint) > cameraManager.Dist ? cameraManager.Dist : cameraManager.Eye.distanceTo(closestPoint);
            }

            dist = dist < dd ? dd : dist;
            dist = Math.ceil(dist / (0.1 * 100));
            const _factor = dd + (dist + (zoomEnd.y - zoomStart.y)) * zoomSpeed;
            detail = {
                x: point.x,
                y: point.y,
                d: w.f,
                factor: _factor,
                callback: () => { }
            };
            wheelStart();
        };

        return ((e): void => {
            w = e.detail;
            if (!w) { return; }
            zoomEnd.copy(zoomStart);
            zoomStart.y -= w.f * 0.00025;
            xy = that.getMouseOnScreen(w.x, w.y);
            that.validatePickingIntersection(that.get2dMouseOnScreen(w.x, w.y), callback);
            zoomStart.copy(zoomEnd);
        });
    }