public function zoomScale( 
   x : int,
   y : int,
   Delta : double,
   postRedrawTimeout : int
);

Parameters

x

The x value of the action's center in pixels relative to upper-left corner of web control.

y

The y value of the action's center in pixels relative to upper-left corner of web control.

Delta

The multiplier that will be applied to the scale action.Set a value between 0 and 1 for zoom out or greater than 1 for zoom in

postRedrawTimeout

Defines how much time will the component wait before redrawing the document.Set it to 0 in order to redraw the view immediately.Set it to -1 for no screen refresh.

Reference