code: function(options) {
          OpenLayers.Control.Panel.prototype.initialize.apply(this, [options]);
          this.addControls([
              new OpenLayers.Control.ZoomIn(),
              new OpenLayers.Control.ZoomToMaxExtent(),
              new OpenLayers.Control.ZoomOut()
          ]);
      }
docs: Constructor: OpenLayers.Control.ZoomPanel
  Add the three zooming controls.
  
  Parameters:
  options - {Object} An optional object whose properties will be used
  to extend the control.