This work but for some reason the 10 digit isbns aren't making it into the final citation... do those get cleaned out or something upstream?

which citation output (how generated) are you referring to?
Zotero does have a clean.ISBN function that might discard the second ISBN, but I'm not sure where it would be run automatically (as opposed to being called explicitly in the translator)

which citation output (how generated) are you referring to?
Zotero does have a clean.ISBN function that might discard the second ISBN, but I'm not sure where it would be run automatically (as opposed to being called explicitly in the translator)

The test case I added, https://archive.org/details/darktowersdeutsc0000enri/mode/2up

When I do ZU.debug(newItem.ISBN) the field has 4 isbns, but when I use the translator file and curl it the isbn 10s are missing. I'm not too bothered by that if you aren't but I was wondering if that was a symptom of something going wrong!

curl -d 'https://archive.org/details/darktowersdeutsc0000enri/mode/2up' -H 'Content-Type: text/plain' http://127.0.0.1:1969/web

[{"key":"9S6E5TKU","version":0,"itemType":"book","creators":[{"firstName":"David","lastName":"Enrich","creatorType":"author"},{"name":"Internet Archive","creatorType":"contributor"}],"tags":[{"tag":"Trump, Donald, 1946-","type":1}],"title":"Dark towers : Deutsche Bank, Donald Trump, and an epic trail of destruction","abstractNote":"x, 402 pages ; 24 cm; \"A searing exposé by an award-winning journalist of the most scandalous bank in the world, including its shadowy ties to Donald Trump's business empire\"--; Includes bibliographical references (pages 367-390) and index; \"A searing expose by an award-winning journalist of the most scandalous bank in the world, including its shadowy ties to Donald Trump's business empire\"--","date":"2020","publisher":"New York, NY : Custom House","language":"eng","numPages":"426","ISBN":"9780062878816 9780062878830","url":"http://archive.org/details/darktowersdeutsc0000enri","libraryCatalog":"Internet Archive","accessDate":"2020-03-06T13:45:37Z","shortTitle":"Dark towers"}]

PS I've linted a little, do you prefer it to go as additional commits in this thread, or as a separate PR?

linting in the same PR, different (non-squashed, obv) commit, please. Thanks!