I had a rather tragic experience due to a water change two nights ago… a few of my smaller cichlids had grown weak and (I suppose had then died) from the low pH level… my Oscars did the honors of cleaning the corpses.. only, my Oscars are no larger than 4 inches each, the carcasses were quite larger than the small minnows they are used to consuming. They have been tank mates with these smaller cichlids for quite some time, so I know they decided to eat them AFTER they died. I wasn’t home when they began their feast, and the last time I saw the Zebra was the morning of, this was late at night when I saw the diminutive cichlid latched in the jaws of my raven and gold/silver Oscar’s jaws. It seemed as if the Oscar was struggling to chew and swallow the zebra cadaver, and with deep observation I noticed the oscar was making NO progress of the consumption of the corpse. I know a lot would say, to take the oscar, and literally pull the dead fish from its mouth, but I prefer to leave things to nature, and allow him to do his own thing… I knew he could breath and him choking wasn’t a concern of mine, but I saw his jaw was getting .. looser. Well, today, over 24 hours later, no zebra fish, and the Oscar’s mouth is completely empty and his jaw is FULLY open, and I know he can’t close it. I tried feeding him the cichlid flakes, and he made a great attempt to sucking them in, but I saw small pieces falling out of his mouth, and he wasn’t spitting them out either… So I threw a small minnow in, and sure enough, he lunged for it.. however it took him a long time to kill it, considering he couldn’t bring his lips down onto the fish… after a while I think he gave up and spat it out… could this be just a strained jaw from holding such a large piece in his mouth for over a day? Or could it just be a broken jaw? He’s losing a color, and I can tell he’s super stressed… any idea of what to do? 
