inside that zip file is another zip, it isn't a folder even if Mac OS may be telling you it is
So you just need to unzip BANGLEJS2.zip and then upload the single file that's inside it - which I would do using the Advanced mode of https://banglejs.com/apps/?id=fwupdate not the Web IDE (as generally it's safer/faster).
If you've got an Android phone you may find it's easier to use that to do the firmware update as it won't pretend that the file inside BANGLEJS2.zip is a folder when it isn't.
Espruino is a JavaScript interpreter for low-power Microcontrollers. This site is both a support community for Espruino and a place to share what you are working on.
I just checked and it should be ok - there's no need to re-zip or anything:
So you just need to unzip BANGLEJS2.zip and then upload the single file that's inside it - which I would do using the
Advanced
mode of https://banglejs.com/apps/?id=fwupdate not the Web IDE (as generally it's safer/faster).If you've got an Android phone you may find it's easier to use that to do the firmware update as it won't pretend that the file inside BANGLEJS2.zip is a folder when it isn't.