Zotero has several Vancouver styles. Visit https://www.zotero.org/styles and search for Vancouver. You will see the options with examples.

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Oops. Someone will need to tell you more. The in-text examples don't indicate punctuation/cite placement. Worst case someone will tell you a simple way to edit an existing style to meet your needs. You should post again and say precisely which Vancouver style you are using.

Sorry. I should ignore my false memory and test before offering a suggested solution.

There's no easy way to switch the position of Zotero citations vis-a-vis punctuation. One could write a Word macro, but that's not trivial to do if you don't program VBA anyway

I just looked at a few examples of journal style guides and examples of printed articles. I also looked at manuscripts that were sent to me for review. All have the citation numbers outside the punctuation.

@adamsmith shouldn't all cite numbers be outside the punctuation? See:

https://jamanetwork.com/journals/jama/fullarticle/2675529

http://injuryprevention.bmj.com/content/early/2018/03/16/injuryprev-2017-042651

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I'm now on my tablet and in transit so can't test. If I click to insert a cite and the cursor is outside the period at the end of a sentence, does Zotero move the cite to before the period (or in the case of quotations, to before the end quote)? I don't remember it that way.

Yes that seems to work OK - I will just manually move around the punctuation - Zotero seems to keep it like that after I have refreshed the document. Thanks!