You cannot exactly convert ZIP archives to ISO format. However you can create ISO compilation for burning that contains .zip archives. This can be nowadays done with any almost any ISO preparation tools. Otherwise it seems no ZIP to ISO conversion is possible.
Convert WinZIP Compressed ZIP archive to CD/DVD/HD DVD/Blu-ray disc ISO binary image.
We have found one software suitable in our database for this conversion.
Apple macOS / Mac OS X software - convert zip to iso on OS X
A dedicated utility for DMG format, DropDMG is the easiest way to create Mac OS X disk images. Just drag and drop a folder or file, and DropDMG will create an image in .dmg, .img, or .smi format—or a Tar, Zip, or StuffIt archive.
Convert from zip file
to iso file
The table with program actions contains information about what each program is capable of doing with their files. This may be a good pointer for further searches for certain file conversions and help you find the converter you are looking for if our search result is insufficient for you. However, it is far from perfect and may sometimes show results which are not really usable because of the nature of the software handles the files. So a conversion that appears as possible, just because of matched actions, may in fact not be possible.