I split the issue with ZipArchive into a new Topic here: http://forum.ait-pro.com/forums/topic/class-ziparchive-not-found-in-installation-php-on-line-259/
At this point, create a temporary Administrator login to the site and send it to edward at ait-pro dot com. In general, a “Cannot redeclare” php error means that a function is seen twice. Could be caused by having duplicate functions, files or a file is being loaded twice (Proxy/routing/CDN/Cloudflare/Cache issue/problem). There are some other causes of this type of php error, but in this particular case, these 3 things would be the only relevant causes of that error.