- Zend_Auth provides the authentication protocol for the users using many methods whereas; Zend_Acl is used for authorization purpose.

- Zend_Auth uses the methods like LDAP, OpenID and HTTP to provide the authentication, whereas Zend_Acl uses Access Control List for authorization.

- Zend_Auth provide the authentication in the form of verifying and providing the credentials for the user’s system, whereas Zend_Acl uses list of roles that is being implemented only those who are authorized to it.

- Zend_Auth provides an environment to the system through which user who is authenticated for use, whereas Zend_Acl performs some operations on the specific resources that need to be written on the system.

- Zend_Auth supports the authentication platforms features, whereas Zend_Acl supports the advanced definitions with features of multiple inheritance and other similar features.