Regarding possible future changes to this plugin.
It is not language-friendly as implemented.
I would suggest that the slideshow start/stop texts are moved out of the admin and into a language file along with new constants to use with the jscript override options in includes/classes/zen_colorbox/options.php
for these texts.

slideshowStart: "start slideshow",
slideshowStop: "stop slideshow",
current: "image {current} of {total}",
previous: "previous",
next: "next",
close: "close",
xhrError: "This content failed to load.",
imgError: "This image failed to load.",

documentation
The readme is a bit minimal.
I would add links to this thread and a much more prominent mention that the original authors page has a great deal of useful information there.
A note to point out that the jscript plugin offers many options which can be overridden by placing the same parameters/options in this file:
includes/classes/zen_colorbox/options.php