All those regions 55, 250, 253 and 254 are available on the zumo. Hopefully they are big enough to take the bin files from the aero's firmware. I've made a composite aera RGN with the boot.bin from zumo and the HWID retained as 924. This is still a time where you can back out and there'll be no hard feelings. From here on you're in uncharted territory and the risk is entirely yours. The devices have almost identical hardware but the slight difference in PCB P/Ns may be significant or not. So, on the strict understanding that although I feel we can at least recover it as a zumo if it gets bricked, the risk is still all yours. If you end up with a hard-bricked device you'll get my symphathy but that's all, so we proceed on that basis only. Look behind the spoiler:
Spoiler:
  • Open the zip file anywhere convenient on your PC, desktop will do: [Only registered and activated users can see links. ].
  • Open the folder "zumo660_to_aera5xx". Drag 0924.rgn onto Updater.exe and it will open with the RGN loaded. Enable 'USB Device', leave the GUI visible.
  • Connect a USB cable directly to a rear port of PC, don't use a hub.
  • Put the zumo in preboot by holding the lower left hand corner of the screen and connecting the USB cable to it, keep watching Updater's window next to USB Device.
  • Immediately you see the device details appear, press OK or hit Enter key on your kb.
  • Keep holding the screen with steady pressure until the flash finishes.
  • Cross your fingers that it boots as an aera.

Good luck!