The tank redesign trick
One approach that can work with problem cichlids such as angelfish is to reset the fishes’ territorial instincts by rearranging the tank decor.
Take the angels out, and place them in a bucket filled with aquarium water and covered with a towel to keep it dark and warm. Now rearrange all the rocks and plants in the tank so it looks completely different.
After about an hour has passed with the angels out of the tank, carefully reintroduce them as if they were new fish you’d just brought them home from the shop. Acclimate them to the new conditions carefully, adding some aquarium water to the bucket to minimise temperature or water chemistry differences. Leave the lights off for the rest of the day, so the fish can slowly explore the tank in the dark – this will be less stressful for them by making them feel less exposed.
The fish will treat the tank as a new bit of the river, and figure out a new social hierarchy from scratch. With luck, it’ll be a hierarchy with different territorial boundaries that might make it easier for other fish to co-exist with them.
The biggest risk is that any mated pair bond will be broken, but unless you were planning to spawn your angels sometime soon, that shouldn’t be a problem. Sooner or later the same or another pair will form.