I have just wasted a couple of hours because the zipflow commit
used here was not the one I used in the independently checked
out tree, so I thought we had had this commit, but had not:

commit c4622bfba95577a24e34112934afffeb3cc2f822
Author:     Mark Adler <madler@alumni.caltech.edu>
AuthorDate: Tue Jan 3 04:08:51 2023 -0800
Commit:     Mark Adler <madler@alumni.caltech.edu>
CommitDate: Tue Jan 3 04:12:37 2023 -0800

    Fix bugs in zip_data() for large lengths.