scope.$on('highchartsng.reflow', function () {
  chart.reflow();
});

$scope.$watch("someElement", function(nV,oV){
  if(nV===oV) return;
  $scope.$broadcast('highchartsng.reflow');
});

// This doesn't work when I add it to the directive..
scope.$on('zoomOut', function() {
  chart.zoomOut();
});

// And broadcast the change from a scope in the controller
$scope.$watch('someElement', function(nV,oV){
    if(nV===oV) return;
    $scope.$broadcast('zoomOut');
});