This issue is raised in the public comment at <http://lists.oasis-open.org/archives/office-comment/200910/msg00027.html
1. In ODF 1.2 Part 3 Packages draft-11-editor-revision, section 1.3, the normative reference for the Zip specification is given as
[ZIP] Info-ZIP Application Note 970311, ftp://ftp.uu.net/pub/archiving/zip/doc/appnote-970311-iz.zip,
This same reference has been used in the OASIS Standards for ODF 1.1 and in ODF 1.0 Second Edition Committee Specification (and thereby IS 26300)..
2. The reference for Zip, ftp://ftp.uu.net/pub/archiving/zip/doc/appnote-970311-iz.zip
in ODF 1.2 Part 3 draft 11 is non-resolvable. The content previously reachable at that location has no clear provenance nor authority.
3. For ODF 1.0, the reference for Zip is
[Zip] ZIP File Format Specification, http://www.pkware.com/products/enterprise/white_papers/appnote.txt,
PKWARE Inc., 2004.
This reference is more authoritative but non-specific. Also, it has been pointed out in the public comment at http://lists.oasis-open.org/archives/office-comment/200910/msg00034.html
that particular URL is no longer resolveable. I presume, from the date, that the referenced APPNOTE version was 6.2.0.