Oxford Brookes university provides BroookesHarvard.ens file support for endnote but no support provided for the zotero. The link for the file is : https://shsc-int.brookes.ac.uk/documents/view.php?fDocumentId=110

https://github.com/citation-style-language/styles/wiki/Requesting-Styles
though my interest in coding another Harvard style for a UK University is rather limited - there are a dozen of those already and it's just getting silly. Which means that you're probably better of trying to do this yourself or finding someone else who is willing to:
http://www.zotero.org/support/dev/citation_styles/style_editing_step-by-step

sorry - I do this for free and in my spare time. I set priorities according to what a) I feel like doing b) what I consider reasonable requirements and c) what will be widely useful for people.

This falls very low an a)&b) and relatively low on c).

The coding probably isn't terribly hard to do so you should considering trying this yourself.