Production
Zines don't really have idle times.
A lot of mods will schedule a zine and assume there are times when you can dip out and focus on the other twenty zines you have going on, but if you are acting as the "head mod" or overall project manager for a zine, and really unless you've decided only to do a very specific set of tasks, you're on call during the entire time the zine is running.
When you run a zine, be ready to:
Have frequent discussions answering questions from applicants, contributors, potential buyers
Stay on top of applications as they come in -- it is easier to evaluate in smaller batches, at least for initial screenings, than to leave it all until the last minute
Check in on contributors and follow up with those who have gone quiet
Post frequent reminders on what comes next, both to contributors and potential buyers
Keep your socials active during the creation phase to keep interest in your project alive
Finalize decisions about pricing and bundling
Market and sell your zine
Create graphics for future announcements/marketing efforts
Lay out non-content pages in your zine (Table of Contents, Credits, etc)
Generally anticipate what might come next, and prepare for it