Below are the steps:
Create a file “phpinfo” in an account:
<? phpinfo(); ?>
and check it using a browser, you should see, you have Zend Optimizer installed.
If not, you can opt for /scripts/easyapache or
Download Zend Optimizer from https://www.zend.com/store/free_download.php?pid=13
and install it on your server.
Steps to install:
# tar -zxvf ZendOptimizer-2.1.0a-Linux_glibc21-i386.tar.gz
# cd ZendOptimizer-2.1.0a-Linux_glibc21-i386