They’d like the development of housing stopped and the site returned to being a zoo, a garden or a virtual reality zoo vs housing. None of the proposals seem to have much merit or an actual plan in mind but they can air objections and they’ve clearly been effective in doing so to establish a need for a review.
The development can’t proceed now as an application for the judicial review of the councils decision will need to be processed. If the application to have one is approved it’ll follow that or it may be rejected. This link explains about JRs. Until that process concludes nothing will progress. It doesn’t impact the new site in planning terms.
Judicial review - Courts and Tribunals Judiciary