Unable to Zoom

I'm using this script and I am unable to zoom in and out.

// -----JS CODE-----

// @input Component.SpriteVisual billboardSpriteA

// @input Component.SpriteVisual billboardSpriteB




var audioComponent = null;

var toggle = false;




function onTurnOn( eventData )

{

global.touchSystem.touchBlocking = true;

global.touchSystem.enableTouchBlockingException("TouchTypeDoubleTap", true);

global.touchSystem.enableTouchBlockingException("TouchTypeSwipe", true);




toggle = false;

toggleBillboard();

}

var turnOn = script.createEvent("TurnOnEvent");

turnOn.bind(onTurnOn);




function onTap( eventData )

{

toggleBillboard();

}

var tap = script.createEvent("TapEvent");

tap.bind(onTap);




function toggleBillboard()

{

if( !script.billboardSpriteA || !script.billboardSpriteB )

{

print( "TOGGLE BILLBOARDS: Make sure to set your billboards in the Inspector panel!")

return;

}




// Toggle billboard

if( !toggle )

{

script.billboardSpriteA.enabled = true;

script.billboardSpriteB.enabled = false;

tryAnimation( script.billboardSpriteA );

toggle = true;

}

else

{

script.billboardSpriteB.enabled = true;

script.billboardSpriteA.enabled = false;

tryAnimation( script.billboardSpriteB );

toggle = false;

}

}




function tryAnimation( billboard )

{

// Play animation

var control = billboard.getMaterial(0).getPass(0).baseTex.control;

if( control && control.play )

{

control.play(1, 0.0);

}

}