Zope has this great product that lets you easily use an external editor on your local machine to edit content on your website via the ZMI. The first step is to download the latest ExternalEditor and zopeedit-src package from
here. There are installation instructions available here. Once you have downloaded the packages unpack the ExternalEditor package in the Zope Products folder which an my Debian system is /usr/lib/zope/lib/python/Products. You can unpack the zopeedit-src package in your home directory.

   $ tar zxvf zopeedit-src-0.6.tgz
   $ cd /usr/lib/zope/lib/python/Products/
   $ sudo tar zxvf ~/ExternalEditor-0.6.tgz

Then restart Zope

   $ sudo /etc/init.d/zope restart

If you log into the ZMI you should now see a pencil icon next to images, templates and other content.

The next step is to set up zopeedit-src and configure your browser to use this application to open your Zope Content. You then customise the zopeedit config script to open the different content types in the editors of your choice, the gimp for images, gvim for text files for example.

The documentation that comes with this product is quite good and explains how to install and set up the ExternalEditor and the Zopeedit packages that you need to get this to work.

You install the ExternalEditor product in Zope on your server and the Zopeedit package which is basically a python script on the local machine and then configure your browser to open Zope objects using that python script. Read the documentation for more details.