I was trying to import a large (about 11,000 entries) Endnote file as XML. In the middle of the import, an error occurred saying "Javascript has run out of memory". Incident number 1924709054.
This means what it says -- Zotero isn't the most memory-efficient app on export and is running out of RAM on export; it's possible that you'd have more luck on a machine with more RAM, but Zotero is a 32-bit app on Windows, so I think there are hardware-independent limits.
Since Endnote XML doesn't preserve collections anyway, I'd suggest just doing this in 2-3 chunks.
Thanks for the advice about importing in chunks. I am trying that now. The confusing issue is that Windows 10 Task Manager states that I am only using 6.3 of 16 GB. I am using zotero 5.0.53.
Since Endnote XML doesn't preserve collections anyway, I'd suggest just doing this in 2-3 chunks.