I am in the process of eliminating a number of components doing different tasks as I have found the different directions developers are heading in can cause major interoperability issues and more work.
Part of this process has been to swap out K2 and Jreviews for Zoo, something I wanted to do with jreviews for a while simply because it was not cost effective for my needs.
One thing major missing Joomla is a reviews component that is freely available so I set out to make Zoo work in this regard, by allowing multiple rating elements is seems like a good base but unfortunately a calculation of all ratings is sadly missing and fortunately I found this extension which (kinda) does a simplified version of this.
Instead of mirroring the rating stars it is output via text, very basic though and so far I have not found it easy to modify without needing to code, this is it's major shortfall though as it simply output's a number of the review total - no way to edit the code to append or prepend text to beautify it slightly.
If the developer could contact me I will happily make a couple of small suggestions that would make this really useful for a wider audience.
If a star rating could be selected as an option that would make it the perfect solution for turning Zoo into a review component as each rating element can be shown as a total and this would really look great in modules.
Other than that, with a little bit of creative implementation is can be used but alas for now only as text and only very basic.