They are visible, you can test this yourself. Open a password-protected zip with 7zip and it’ll show the file list even without entering the password. The “encrypt file names” checkbox doesn’t even appear when creating an archive if the zip format is selected, so I’m not sure the format supports it.
That was what someone claimed but it isn’t true. Filenames are not accessible in an encrypted zip.
They are visible, you can test this yourself. Open a password-protected zip with 7zip and it’ll show the file list even without entering the password. The “encrypt file names” checkbox doesn’t even appear when creating an archive if the zip format is selected, so I’m not sure the format supports it.