The problem isn't __MACOSX, which calibre does not care about but that the comics.txt file is not at the top level of the zp file. Instead it is under the xxxHolic sub-directory. Below is the output from running unzip on the attached zip file
Code:
Archive: xxxHolic.zip
Length Date Time Name
--------- ---------- ----- ----
0 2017-07-07 07:05 xxxHolic/
6148 2017-07-07 07:06 xxxHolic/.DS_Store
0 2017-07-07 07:09 __MACOSX/
0 2017-07-07 07:09 __MACOSX/xxxHolic/
120 2017-07-07 07:06 __MACOSX/xxxHolic/._.DS_Store
111 2017-07-06 10:28 xxxHolic/comics.txt
498 2017-07-06 10:28 __MACOSX/xxxHolic/._comics.txt
4030144 2017-07-06 09:36 xxxHolic/Xxxholic-1.1.cbz
316 2017-07-06 09:36 __MACOSX/xxxHolic/._Xxxholic-1.1.cbz
1889220 2017-07-06 09:36 xxxHolic/Xxxholic-1.2.cbz
316 2017-07-06 09:36 __MACOSX/xxxHolic/._Xxxholic-1.2.cbz
3412924 2017-07-06 09:35 xxxHolic/Xxxholic-1.cbz
316 2017-07-06 09:35 __MACOSX/xxxHolic/._Xxxholic-1.cbz
1246802 2017-07-06 09:36 xxxHolic/Xxxholic-2.cbz
316 2017-07-06 09:36 __MACOSX/xxxHolic/._Xxxholic-2.cbz
--------- -------
10587231 15 files
See the line
111 2017-07-06 10:28 xxxHolic/comics.txt