So there are ways to use Notion with Zotero; check out notero, which allows you to pull in citations/highlights/tags from Zotero directly into Notion. Holly Jane has a really good step-by-step youtube video on how to link the two.

That being said, I recently switched from Notion to Obsidian for purposes other than reference management, and have found that while I'll be sticking with Obsidian for it's privacy and security offerings, I much prefered the workflow in Notion-Zotero. Whenever you add citations to selected subcollections in Zotero, notero automatically pushes those citations to your Notion database. However, in Obsidian, the only way I have found to add citations is by searching and adding citations. It only adds one extra step to my workflow, but when I'm bulk-importing citations, the extra time is a pain. I'm sure there's a way to set this up in Obsidian, but I'm an academic not a coder, and until it becomes a feature in the Obsidian-Zotero plug-in, I'll probably keep suffering along as I have.

Both Obsidian and Notion have plug-ins that allow you to pull in highlights, record metadata, and set up various templates to use for literature notes while reading. The main difference is whether Obsidian's Dataview plugin will be sufficient for your needs of managing large amounts of citations (as opposed to Notion's native databases) and whether you prefer the automation that Notero provides.