I've made a simple API to controll zimbra with for PHP or even GET params. It isn't full ready or tested yet, but the main tasks works fine now. Maybe the one or other want to extend, test or improve it (or translate it, currently its written and commented in German...)
theres also no authentification now (e.g. md5), only an restriction for local Ip's.
so long, have fun
p.s.: you shouldn't forget .htaccess