Normally your Mac should have an app called 'Archive Utility'. It usually starts automatically and unzips your zip-file when you download one into the download folder, you should then see a folder with the same name as the zipped file show up in the same location. So quite possibly, you have these folders already sitting in your download folder.
The other way you can unzip it is by simply double-clicking the zip-file and a folder of same name should magically appear in the same location, in your case the desktop.
Then mount an SD-card with no more than 32GB. If you have not formatted it in another way, it will most likely be FAT32 format. You can verify this with DIskutility.
Make sure there are no other files on the SD-card, then, on your desktop, open the PART1 folder, select all content, cmd-C (copy it), open the SD card and cmd-v (paste it). Now all the files that you saw in the PART1 folder should be on your SD-card, which you can now eject.
Now do the same procedure with a <=32GB USB-stick and the content of the PART2 folder.
Eject it too and then follow the Furuno update instructions.
