Knowing the immediate history is helpful but not essential. Bootlooping devices are always harder to catch in preboot because there is only a brief period when it's able to be seen in Updater.exe before it drops the connection and starts again. I recovered a bootlooping nuvi 2797 which is the same hardware as your dezl 760 and it was a pain to flash but persistence paid off. Unless your device has physical damage to it's internal flash it can be recovered. Check it's battery has reasonable charge first and then try this procedure:
  • Ensure the device is fully OFF. You may have to hold down the power key for 10 to 30 seconds until it turns off.
  • Plug a suitable USB cable directly into a USB2 port of your laptop (Not a USB3 port and don't use a hub). If you can find a desktop PC to use, that's better still but make sure to use a REAR USB2 port only.
  • Load the Cure firmware to Updater.exe and select the radio button next to "USB Device". Leave the GUI visible on your computer with your mouse cursor positioned over "OK" button.
  • Hold the upper LH corner of the dezl's screen (use your left thumb is best) and while watching the window next to 'USB Device" quickly plug the microUSB end into the dezl.
  • IMMEDIATELY you see the device details appear in the window either click "OK" on Updater's GUI or just hit your computer's Enter key.
  • Keep firmly holding the screen until 'Loader' or 'Software Loading' appears on it at least, if unsure hold until the flash is reported as successful.
  • If you miss it start again ensuring the device is fully OFF firstly.

I've had bootlooping devices which could only have a flash started by hitting the Enter key with my right elbow because the opportunity time to initiate Updater was so brief. It seems to vary, sometimes it's much more leisurely.