I'm coming at this from a US perspective since that's where I am.
If you wanna get super technical no, zines are not legal. It doesn't matter if they're sold for charity or given away or what. Technically all fanart is copyright infringement and the copyright holder is legally allowed to sue you over it.
That said, it's kind of just one of those things that is technically against the law but really unlikely to get you in trouble unless the copyright holder is particularly litigious and even then you'll get a cease and desist before they actually take you to court. For most large media companies the amount it costs to sue a fanartist is way more than whatever money they might get from the lawsuit. Also if you wanna piss off your fanbase suing your fans is a good way to do that. So the majority of companies just kind of let it slide unless someone is running a huge operation or using a trademarked logo or something.