ETOPS stands for Extended-range Twin-engine Operational Performance Standards, EDTO stands for Extended Diversion Time Operations. And this would be the main difference.

Another difference between EDTO and ETOPS approach is that EDTO covers extended range operation of aircraft with more than two turbine engines, such as those with three and four engines.

one more relevant aspect is the maximum diversion time allowed under EDTO. With ETOPS, some records say some aircraft have gotten ratings up to 370, like the Airbus 350, for example. Actually, some rumors suggest Airbus was seeking a rating of 420 in 2014, but nothing has been confirmed. However, according to EDTO, the maximum diversion time must be 180 minutes, based on ICAO guidance.