Caching with ZendPlatform

I’ve been trying to cache WordPress installations with ZendPlatform from Zend.com
It doesn’t work, the problem is in the wp-includes/template-loader.php file, everything ends with the exit; command.
exit = die, which indicates an errorcondition, exit(0) schould fix the problem but doesn’t, apparently ZendPlatform doesn’t look at the returnstatus ??
I was wondering, would it harm wordpress to replace all the “exit”‘s with “return” ?
It solves the cachingproblem.