ZIP is an archive (container). TTF is a font format. You cannot turn a ZIP into a TTF without extracting.

While you might also see files inside your ZIP, TTF remains incredibly popular because:

If you downloaded a font and it came as a ZIP, the TTF file is already inside it.

Right-click the ZIP file → select "Extract All..." → open the new folder to find your .ttf file.

That’s it. You’ve successfully “converted” your font.