Many thanks for your help.

Locate ZendOptimizer through out the server leads to 0 result. I
assume that software is not installed on the server.

Strace Function for further enquiries :
The fact is : the command is not recognized by the current
Trying multiple strace use leads to :
-bash: strace: command not found

You idea was that we get a problem with the httpd process ? That
process consumes 40 to 80 % of the available CPU.

Again, all my thanks.