I’ve got two programatically constructed ods files; LibreOffice thinks both of them are corrupted and I can’t figure out why. One of them can be recovered and one can’t; the one that can’t is Zip64.
This guy’s claiming that Zip64 is supported by the spec: https://www.decalage.info/files/JCV07_Lagadec_OpenDocument_OpenXML_v4_decalage.pdf
The heart of this question turned out to be Zip64 should work but doesn’t due to a bug. See comments.