jquery в head'e - ZOO 2.х

  <script type="text/javascript" src="/media/zoo/libraries/jquery/jquery.js"></script> // вот это в особенности
  <script type="text/javascript" src="/components/com_zoo/assets/js/default.js"></script>

<script type="text/javascript" src="/"></script>

if (!JFactory::getApplication()->get('jquery')) {
	JFactory::getApplication()->set('jquery', true);
	JHTML::script('jquery.js', 'media/zoo/libraries/jquery/');
}

// add default js
$zoo->document->addScript('component.site:assets/js/default.js');

$this->app->system->document->addScript($this->app->path->url('libraries:jquery/jquery.js'));

class DocumentHelper extends AppHelper {

	/*
		Function: addStylesheet
			Add stylesheet to the document.

		Parameters:
			$path - Path to CSS file

		Returns:
			Void
	*/
	public function addStylesheet($path) {
		$this->app->system->document->addStylesheet($this->app->path->url($path));
	}

	/*
		Function: script
			Add javascript to the document.

		Parameters:
			$path - Path to js file

		Returns:
			Void
	*/
	public function addScript($path) {
		$this->app->system->document->addScript($this->app->path->url($path));     //Пробовал удалять - не помогает
	}

	/*
		Function: __call
			Map all functions to JDocument class

		Parameters:
			$name - Method name
			$args - Method arguments

		Returns:
			Mixed
	*/	
    public function __call($method, $args) {
		return $this->_call(array($this->app->system->document, $method), $args);
    }
	
}