Bug Summary
Local is not very intelligent at importing existing sites, it is too particular about the makeup of the zip.
Steps to reproduce
Take an existing WP site to create a zip file. Use a tool like Table Plus to export the database as an .sql file. Select both files and compress them again into a zip file.
It is this point when it comes to importing the site that Local is too stupid to recognise a zip within a zip file. This is by far the most expedient way of preparing a zip file and yet local doesn’t recognise that there’s only one zip file and a sql file contained in the outer zip file. Local should be able to recognise this circumstance and extract the zip inside the zip.