To load a custom language, simply include that language script before MarkEdit.

<script type="text/javascript" src="/js/lang/markedit.lang.zh.js"></script>
<script type="text/javascript" src="/js/jquery.markedit.js"></script>

If you are interested in creating a translation script, the markedit.lang.template.js is included for your convinience. Note that any object not included in the translation will be auto-populated by English.