Under mz_strm_os_posix.c, mz_stream_os_open() checks for
(mode & MZ_OPEN_MODE_APPEND) at line# 82.
But under mz_compat.c, zipConvertAppendToStreamMode() at line#50 has a statement
case APPEND_STATUS_ADDINZIP: mode |= MZ_OPEN_MODE_READ
The mode setup in mz_compat won't match the one for stream open.
Can you consider revising the mode to something like:
case APPEND_STATUS_ADDINZIP: mode |= MZ_OPEN_MODE_READ | MZ_OPEN_MODE_APPEND;
Thank you