I notice that ZoteroBib will often not find ISBN numbers that I am searching for, especially for eBooks. But ISBNsearch, for example, will find them. Is this because ZoteroBib is more academically oriented?
Perhaps. The companion question may be to ask how well Zotero finds DOIs on journal articles (e.g. versus a dedicated DOI search tool).
Philosophy aside, the observation indicates that each method a) uses its own search algorithm on the same databases or b) searches different databases.
What you say makes sense but I had hoped that ZoteroBib, from how forum members spoke of it, would be a universal doorway to the world of ISBNs. There I go letting my expectations trip me up again …