I'm not entirely sure if baotoulu is offering an electronic copy of the study guide or an electronic copy of the exam itself.
If it is the study guide then Zend has no issues. Much like any other "book" people are free to share it within the terms of applicable copyright law.
If it is a copy of the exam itself Zend would like to make it clear that this is a violation of the Nondisclosure agreement (NDA) that all students agree to prior to taking the exam. Anyone offering a copy of the question form the exam itself would be considered "cheating" under the terms on the NDA and could result in revocation of any ZCE certificate and/or possible legal action.
In addition anyone who receives a copy of the exam and uses it to study for the test could also be determined to be "cheating" under the terms of the NDA and Zend would be within it's rights to withhold the PHP certification.