zoom in, out and drag isometric land in as3

Code :-
=====

land.addEventListener(MouseEvent.MOUSE_DOWN,moveland);
land.addEventListener(MouseEvent.MOUSE_UP,releaseland);
land.buttonMode = true;
function moveland(event:Event):void
{
event.target.startDrag();

}
function releaseland(event:Event):void
{
event.target.stopDrag();

}
import fl.transitions.*;
import fl.transitions.easing.*;
import fl.motion.easing.*;
var factorZoom:Number;


stage.addEventListener(MouseEvent.MOUSE_WHEEL ,onclick);
factorZoom=1;
function onclick(e:MouseEvent) {
if (e.delta>0) {
factorZoom=factorZoom+0.01;
trace(factorZoom);
} else if (e.delta<0) {
factorZoom=factorZoom-0.01;
}
imageToZoom();
}


function imageToZoom():void {
var overPixelX:Number=land.mouseX;
var overPixelY:Number=land.mouseY;
//
land.scaleX=land.scaleY=factorZoom;
var pixelDifferenceX:Number = (overPixelX - land.mouseX) * factorZoom;
var pixelDifferenceY:Number = (overPixelY - land.mouseY) * factorZoom;
//
var nextX:Number=land.x-pixelDifferenceX;
land.x=checkNewX(nextX);
//
var nextY:Number=land.y-pixelDifferenceY;
land.y=checkNewY(nextY);
}

function checkNewY(checkY:Number):Number {
if (land.height<600) {
return (600 - land.height) / 2;
}
if (checkY>0) {
checkY=0;
} else if (checkY + land.height < 600) {
checkY=600-land.height;
}
return checkY;
}
function checkNewX(checkX:Number):Number {
if (land.width<800) {
return (800 - land.width) / 2;
}
if (checkX>0) {
checkX=0;
} else if (checkX + land.width < 800) {
checkX=800-land.width;
}
return checkX;
}

Out Put :-
=======