I suggest you put your money where your mouth is and show some exampes
of the parse errors you say are being generated when you run Zend
Guard's syntax-checking abilities against the latest version of ZF.
That's the only way to be sure.
Here you go, Zend Guard 4.0.1 is the latest version, php 5 compatible:
/usr/local/Zend/ZendGuard-4.0.1/bin/zendenc5
Zend Guard (PHP 5) v4.0.1 (c) Zend Technologies, 1999-2006
/Zend/Request/Interface.php: Interface.php(line 111): parse error,
expecting `''' or `T_VARIABLE'
Encoding of '/Zend/Request/Interface.php' failed.
/Controller/Action.php: Action.php(line 92): parse error, expecting
`''' or `T_VARIABLE'
/Zend/Controller/Action.php' failed.
Zend/Controller/Action.php: Action.php(line 161): parse error,
expecting `''' or `T_VARIABLE'
/Zend/Controller/Action.php' failed.
/Zend/Controller/Router/Interface.php: Interface.php(line 61): parse
error, expecting `''' or `T_VARIABLE'
/Zend/Controller/Router/Interface.php' failed.
Zend/Controller/Router.php: Router.php(line 61): parse error,
expecting `''' or `T_VARIABLE'
Encoding of '/Zend/Controller/Router.php' failed.
/Zend/Controller/Router.php: Router.php(line 86): parse error,
expecting `''' or `T_VARIABLE'
Encoding of '/Zend/Controller/Router.php' failed.
Zend/Controller/Request/Abstract.php: Abstract.php(line 188): parse
error, expecting `''' or `T_VARIABLE'
Zend/Controller/Request/Http.php: Http.php(line 613): parse error,
expecting `''' or `T_VARIABLE'
Zend/Controller/Dispatcher.php: Dispatcher.php(line 88): parse error,
expecting `''' or `T_VARIABLE'
/Zend/Controller/Dispatcher/Interface.php: Interface.php(line 84):
parse error, expecting `''' or `T_VARIABLE'
/Zend/Controller/RewriteRouter.php: RewriteRouter.php(line 63): parse
error, expecting `''' or `T_VARIABLE'