If your contact-us page is broken, you probably have incorrectly altered one or more files, including but not limited to:
/includes/modules/pages/contact_us/header_php.php
/includes/languages/english/contact_us.php
/includes/templates/your_template/templates/tpl_contact_us_default.php
Maybe you need to replace those files with the originals?
Maybe turning on the debug-logging tool mentioned in my previous post might shed some light on the specific PHP errors you've got which are causing the problem.
Maybe comparing those files with the originals that come with Zen Cart might identify causes.
Granted, there's not much more we can do to help you without knowing what version of Zen Cart you're using, whether it's been upgraded, from what version, a list of all addons you've added, your PHP version, and even what you're using for your email settings.