When we upgraded Zenodo in October 2023, we changed to a new REST API while still supporting the legacy API. The legacy API is the one which is documented on Zenodo.
Upgrade blog post: https://blog.zenodo.org/2023/10/13/2023-10-13-zenodo-rdm/
Documentation https://developers.zenodo.org/
The UI uses the REST API endpoint which is documented on inveniordm.docs.cern.ch and we're working on improving this:
Official documentation: https://inveniordm.docs.cern.ch/reference/rest_api_index/
Experimental OpenAPI documentation: https://inveniosoftware.github.io/invenio-openapi/