Language field is static, not adapting to the language of Bibliography
I have items in various languages in my library. I filled out the Language field. Now ideally I would just enter language codes in that field and when the .bib is called from LaTeX it would expand to "English" when I have bibliography in English and it would expand to "Englisch" when I have a bibliography in German. This doesn't work like that and manually changing that field every time depending on the language I'm writing is not an option. How can I get rid of that field entirely? Either for all items in Zotero or in my citation style authoryear-ibid?
How to mark a bilingual publication?
Short answer: You can’t, at least not via Zotero’s “Language” field.
Zotero’s “Language” field, just like biblatex’s “langid” field, is not supposed to describe the language(s) used inside the work in question (e.g., “Greek and English”), but merely specifies the (primary) language of the bibliographic record (hence no more than one language tag is allowed here by Zotero as well as by biblatex) – which is relevant for case conversion of the title and (at least when using latex) hyphenation.
(Zotero, quite correctly, maps the “Language” field to biblatex’s “langid” field upon export, but the purpose of Zotero’s “Language” field seems to be misunderstood at times; this might be something that could be explained more clearly in Zotero’s documentation …)
biblatex does have a “language” field that is indeed used to describe one or more language(s) used inside the work, but there is no Zotero counterpart – though it’d be great to see that kind of functionality added to Zotero in the future.