to zero in
to focus attention: We need to zero in on the client’s exact expectations for this software. Don’t bother with any additional functionality at this stage.
to zip up
to keep something quiet: Keep this matter zipped up will you? It’s still highly confidential.
to zoom in
to magnify an image: Can you zoom in on that part of the picture? I want to read what the poster says.
to focus attention: Let’s now zoom in on the company’s debt problem.
Common Mistakes in Business English 
“Zero in” and “zip up” are slang, not “business english” They should not be used in any contract or other legal document used for business purposes