My partner understands your sentence, and I've now asked a 2nd native Czech speaker to translate 'the cat is eating the food' they wrote ' Kocka ji to jidlo' they also understand zere is used for animals, but it is viewed as eating like a animal, which in turn can be viewed as impolite. So although your native team are also being correct the other way should also be recognised. Its a bit like me teaching someone English by saying 'One does one's best' instead of saying "I do the best I can' both correct but the 1st one would make you look pompous. However I must congratulate you on your quick response, as usually when I ask a question it's left to several different users to give several different explanations, which is of no help whatsoever, and the very reason I won't use the paid version. Maybe in future I should question the DuoLingo algorithm to ensure prompt reply, I bet your English course doesn't use correct English but everyday English something I would want from any language course.
Most courses on Duolingo teach the correct and rather formal language. Especially in Czech there are two completely different versions of the language: standard and common. Only the last unit of this course tackles the Common Czech, all the rest is about the written official standard language.