Which style and for what purpose? There are a couple of styles that do this already, see e.g. https://www.zotero.org/styles?q=id:american-medical-association-alphabetical&dependent=0 If you want a custom style, you can look at this as a template. If an existing style is wrong or you're looking for a style for a specific journal, you can just request that.
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https://www.zotero.org/styles?q=id:american-medical-association-alphabetical&dependent=0
If you want a custom style, you can look at this as a template. If an existing style is wrong or you're looking for a style for a specific journal, you can just request that.