you are trying to create a Zend_Db object with MySQL adapter, I think. there is no MySQL adapter by default for Zend Framework. you should use MySQLi adapter, or Pdo_Mysql.
checkout your code, where you are creating your Zend_Db object. pass in 'Pdo_Mysql' as your adapter name, instead of 'Mysql':
$_db = Zend_Db::factory('Mysql', $configArray );
// uses Mysql adapter, which is not available by default.
$_db1 = Zend_Db::factory('Mysqli', $configArray );
// uses Myqli adapter, but needs php_mysqli extension to be installed.
$_db1 = Zend_Db::factory('Pdo_Mysql', $configArray );
// uses Pdo Myql adapter which is much better, but needs PDO to be installed, which most of times is installed.
you can write your own adapter for Zend_Db. write a class and extend the Zend_Db_Adapter_Abstract. but there are some problems to implement Mysql adapter, because PHP_MySQL extension (that will provide PHP with mysql_* functions) does not support many features (like client stored procedures, ...). so you can not implement all of methods that other Zend_Db_Adapters have. I've done this before. I wanted to use my application, that used Zend Framework, and I hosted it on a server that PDO and Mysqli were not installed. I implemented a Mysql adapter for Zend_Db, but because I knew which methods are not implemented, I avoided calling those.
the best thing is if you could have PDO installed, and use Pdo_* adapters.