WBB 3.0.x Plugin installation unmöglich

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Fatal error: Can not find functions of the zlib extension

You get more information about the problem in our knowledge base: http://www.woltlab.com/help/?code=11004
Information:

error message: Can not find functions of the zlib extension
error code: 11004
file: /users/wcfx/www/23/install.php (644)
php version: 5.3.1
wcf version:
date: Wed, 13 Jan 2010 20:12:19 +0000
request: /23/install.php
referer: http://wcfx.square7.ch/23/
Stacktrace:

#0 /users/wcfx/www/23/install.php(328): ZipFile->__construct('/users/wcfx/www...', 'rb')
#1 /users/wcfx/www/23/install.php(305): Tar->open()
#2 /users/wcfx/www/23/install.php(725): Tar->__construct('/users/wcfx/www...')
#3 {main}