There does not seem to be a Lua binding for that, see:
https://www.zotero.org/support/dev/web_api/v3/start
(KOReader is mostly implemented in LuaJit).
You want to write that binding wrapper for us?
Contact the KOReader project people directly through their public repository.
Here is the (or your) starting point:
https://github.com/zotero/zotero
or maybe better:
https://github.com/zotero