http://zend.com/store/products/optimizer-faq.php#9
How is the Zend Optimizer installed?
UNIX (Linux, Solaris, FreeBSD) & Mac OSX
To install the Zend Optimizer under UNIX or Mac OSX:
1. Execute the following command (and follow the instructions):
./install.sh
NOTE: Be sure to download the Zend Optimizer version that corresponds with the platform you use.
2. If you are running under Apache, restart your Apache Web server. For Apache V1.3, use the commands:
apachectl stop; apachectl start