I have two daily tasks: process todoist inbox and process gmail inbox. So, my method of "inbox zero" consists at looking for at least 5 minutes every day at my Todoist inbox and my gmail inbox.
1. I started looking at my e-mail, if an e-mail leads to an action, I put it in my Todoist inbox, and I archive it. If not, just archive it without generating tasks. With this method, I archive everything everyday, so it is always at zero. I try to always look at my e-mail before doing my todoist processing, so the e-mail may be answered at the same day, however I realize that most often, my e-mails don't demand an action for the same day. It can wait for tomorrow or even later.
2. And everyday I also keep my todoist inbox at zero. If it is something that is quite fast to do (5min), I just do it right away. If it is not I create a task and deal with that the following day.
I think the most important thing is to always keep things updated, and also always putting everything at my todoist inbox!