How do you synthesize research from dozens of sources without losing your mind?

I'm deep in a lit review and I have 40+ tabs open across multiple papers, articles, and references. I know there are connections between them but I can't hold it all in my head. By the time I read source #30 I've forgotten the nuance of source #5. Zotero helps with citation management but not with actually synthesizing what I've read. How do you all do this? Genuinely asking, I feel like I'm drowning.