In general the nutritional value of the food is less affected by microwave cooking, because you can use much lower heating times and it is easy to ensure that the temperature is not too great.

Moreover, at microwaves it is easy to cook without adding water (whenever you are cooking meat or vegetables with high content of water, e.g. potatoes; when not adding water, using a glass vessel covered with a glass lid is normally mandatory), or only by adding a minimum amount of water, which avoids the leaching of water-soluble nutrients.

These properties ensure that food cooked at microwaves in the right way (e.g. without water whenever that is possible) is frequently tastier than when cooked by traditional means. The only exception is for people who like burned food, as this method for degrading food is more difficult to do at microwaves.

While the fact that food is less affected by microwaves than by most other methods of cooking is intuitively obvious, there have been published several research articles where it was investigated the degradation of several essential nutrients, e.g. vitamins, during cooking by various methods, and they confirmed a minimum degradation during microwave cooking, caused by shorter cooking times and lower peak temperatures.

When cooking at microwaves, you normally do not cook everything together, because meat requires different parameters than vegetables and there are 3 or 4 classes of vegetables that require different parameters. So you typically cook the ingredients separately and you mix them after cooking, when you also add ingredients like oil, which should better not be heated.

You can cook multiple classes of vegetables together, if you start with those that require the longest cooking time, and microwave them for the time difference vs. the next class of vegetables, then you add the next vegetables and microwave them for the next time difference, until you add the last kind and microwave again everything for the remaining time.