By XAMPP installation default, I believe it's already running. If you search for [Zend] in your PHP.INI file, you'll see where the modules aren't commented out, so therefore it's loading it.
I think the more appropriate question is how to configure it for what you're trying to do.
It would help if you gave us more info such as what you're trying to achieve with it and what you're trying to do.
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