Ask yourself honestly: should you mod a zine?
Do you have the time? Many mods severely underestimate the time it takes to run a zine, and make the costly mistake of taking on too many projects that run into each other as a result. While some phases of a project may mean some weeks are less hectic than others, expect 5-10 hours of work a week on average, with hours going up to 15-20 per week for some tasks like formatting and shipping. Also consider that zines will take anywhere between 8 to 12 months total from start to finish, assuming everything goes according to plan. If you aren't ready for the pitfalls of zine modding, these can run even longer. Be realistic about your availability. If you do not have this time to spare, please carefully reconsider.
Do you have the money? I hesitated for the longest time about bringing up a barrier to entry like this, because I do believe fandom experiences should be as accessible as possible. But when you consider that zines involve the time and effort of 20-60 creators producing commission-quality work, it is important to know from the start that you can compensate all your contributors no matter how badly sales go. And sales can go badly! Do not go into zines thinking sales will pay for all expenses automatically. For every zine that manages to sell more than 500 copies, there are a dozen -- maybe more -- that struggle to sell 50. Sales are not guaranteed. This isn't a totally capital-free endeavor. Be ready to pay out of pocket, and if you aren't, then consider pursuing projects that do not require material investment. (How much should you set aside? That's entirely dependent on how much it will cost to produce copies of the zines for the number of contributors you have, and ship it to them free of charge. It's not $100 or $500 -- it's however much your zine costs to make.)
Do you have the experience? Experience does not have to be in running other zines. Experience does not have to be in running other zines. But be sure that you are comfortable enough with budgeting, project management, and communication. Be especially comfortable with handling money and budgeting -- it is a big responsibility, but zine-running is a big responsibility. There's just no sugarcoating around this: you must step up ready to be accountable for everything involved in it.
Do you have the mental energy? Zines are fun fandom projects, but you need a certain kind of mental fortitude to handle all the stress that can come with bringing a big project to fruition. This is a project with self-imposed deadlines, so you need to be keeping it on track. You need to remember when things are due, you need to follow-up with the people involved when deadlines are missed. You need to have the mental capacity and sustained interest/dedication to stay on top of this project, and honestly, it is added stress, including many things this guide will not tell you because anytime I've run a project is also the first time I've run into a very specific, unlike-other-situations-before issue! You have to be tough and reasonable, even-keeled and clearheaded to make sound decisions. If your life is already stressful, do not add another stressor on top of it.
Will running this as a fan week, exchange, or big bang work just as well? There are other ways to come together as a fandom, and zines are not the end-all, be-all of participation.
If you answered yes to the first four questions and no to the last, then read on: