Zend Optimizer is it work a try?

I have a server:

Intel Processor: Intel® Xeon® X3450, 4x2x2.66 GHz
RAM memory:   8GB ECC DDRIII

The per day visitors:

100k unique
400k clicks

Basically, 20 domains run from a single script. I do quite often update the script. Daily. I was wondering whether Zend Optimizer is a good option to optimize script perfomance. (even though, I don't feel any discomfort at the moment)

My two main concerns are:

1. Will it actually increase page loading time/decrease server RAM/CPU load? If so, by how much (%)?
2. Isthere a comfortable way, using OS X, to keep original files on Local disk and every time you press save, for the program to automatically encode files and upload them to the server? (I am using Panic's Coda)

In response to your first point. No, Zend Optimizer was only really relevant with php4. Since PHP5, the internal engine/ has been improved such that the optimizer is redundant. What you should look at using if you are not already is APC [1], there is lots of stuff on here and google about it but in short, it caches your code so PHP doesn't have to compile it every time the page is run. (and it makes a MASSIVE difference to code execution speed)

You should also look at running some form of profiler such as XHprof [2] or xdebug[3] on the code so you can see where the bottlenecks are.

You might also want to think about using a different web server such as nginx/lighttpd/apache or fine tuning its configuration

For you second question about Coda - ask it as another question on here or programmers.stackoverflow

[1] http://php.net/manual/en/book.apc.php [2] http://mirror.facebook.net/facebook/xhprof/doc.html [3] http://www.xdebug.org/