Can't reflash esp8266 - 12E after many attemptions
Try following ESP8266: flash module firmware post. I've used those steps on ESP-07 and ESP-01 module several times. There should be no need for resistors unless specifically required by ESP-12 module. If it still fails try to eliminate software issues as the problem by using windows flasher as per the post as that is known to work. Also do not use a breadboard as it can cause issues.

Here's a working schematic for ESP-07 module and by the looks of it it should be the same for ESP-12: