and East African lake cichlids are all cichlids, but you have to ask yourself why one group's in Africa and the other's in South America. It took a long time for those continents to drift apart, and a lot of that time involved radical evolutionary changes in the fish.
come from mineral poor river water that floods a great rainforest. The water is soft and stained with tannins. Discus move through roots and reeds, and are peaceful, delicate sociable fish. They are adapted to an extreme environment - warm extremely soft acid water.
East Africans live in huge lakes full of extremely hard water, They fight for every inch of their limited, really crowded territory. They have a number of adaptations to mineral loaded water, and can't survive in soft or acid water. Their equally extreme natural environment is extremely stable, and their lifestyle is one of pure aggression and battle for territory. They live in huge flocks and constantly battle for dominance.
So no, don't even think about putting them together. There are a dozen cichlid books in the library close to you, or in any good bookstore. Check a couple out. A little time will save you lots of disappointment, and save more than that for your fish.
Kribs are from soft, mineral poor water, but in breeding times are much too aggressive for discus. Their water needs are cooler than those of discus, but the chemistry is about the same. Behavior's the problem.
I never liked keeping other cichlids with discus, although rams would be a possibility. Rummy noses and fully grown cardinals look good with them, and come from the same part of the world.