I have never used Zotero to actually write or edit anything, just store the extracted notes and annotations before going through them in a note attached to the item and then again in a separate note after cleaning them up and outlining in RemNote (you have to export as text and manually shift+select the entire text and then paste it so it will stay pre-formatted, i.e. outlined in case you want to import some parts of it back into RemNote).
I’ve also taken to using concept titles for my notes a la Evergreen notes by Andy Matuschak. In my opinion, there is no need to use manual numbering in a digital Zettelkasten: if your notes are short enough, you may create entry-notes or indices by referencing them wholly; if they get too long, try using titles and again referencing them. Of course, Pro users can mix and match both approaches using aliases.
Can’t say I’ve messed around with Notion much, but the crucial part of Zettelkastening is that all permanent notes are considered to be equal, and the links between them can and should be made and destroyed on the fly as the primary mode of organisation. In other words, the only schema necessary are a list of permanent notes and a list of links between them (the outliner taking care of basic “behind” links and with entry-notes and the index eventually arising as an organised collection of links). Of course, you may augment that if you choose, but trying to go organisation first (top-down) rather than allow the links to build up before formalising them would go against the insight-creation portion of Zettelkasten.
If you are interested in discussing this further, there is a learner group starting up over on Discord, I would say this thread is a bit more specific to the apps involved in Zettelkasten rather than its principles.