Translation:Eat, otherwise we are not going to the zoo.
"or" is to introduces 2 options: A or B. Pick one: A) You eat or B) We don't go to the zoo. In this case "we dont go to the zoo" is an option instead of an adverse consequence of not eating.
"Otherwise" means: if not, if so.
"if not" Eat, otherwise ( if not ) we are not going to the zoo
"if so" Don't be late, otherwise (if so) the doctor is not going to see you.
But the Italian "altrimenti" can be translated as "or [else]" in this context. It's an issue of the Italian word having more than one valid English translation.
And as a side note, I don't think "o" can carry this meaning in Italian, so "altrimenti" would be the best way to translate an English sentence using "or".
It might be something you do idiomatically (e.g. "You, pick up that chair! You, get on the table!"). But as a general rule, the subject of the imperative is implied.in both Italian and English. Including it in a contextless sentence (especially without a comma to set it off) confuses the meaning.
A year later, April 2015, and I was marked wrong for the same answer. I am guessing that they do not follow up on our reports very often. I included the implied "you" and was marked wrong. I wrote, "you eat, or else we do not go to the zoo" and it was marked wrong. Bummer. (yes, I reported it for whatever that is worth)
I can't imagine the context for that. Are you watching someone eat and telling your party that their trip to the zoo is contingent on his finishing the meal?
The imperative just fits more naturally here. Unlike many DL sentences, this one has enough context to make that clear.
"Mangi" should be accepted, but the Italian module on here is notoriously bad at not accepting the formal "Lei" translations of anything. Though, to be fair, this would be an unlikely scenario for you to be addressing someone formally (you generally don't say things like, "Eat, or we don't go to the zoo," to your boss).
"Mangiare" isn't a really good fit here, because we're in the imperative section. While the infinitive can function as a command, it's more often used to express the negative, and it's always more general. You wouldn't generally use the infinitive to address a specific person, but you would use it on a sign for the general public.
The problem with "Lei" on DL is that there's no way for the program to know that you know the difference in conjugation between "tu" and "lui/lei", so it needs to assume you accidentally used the wrong conjugation, since I guess thats more likely than be aware of the "Lei" form. If you want to do well on DL, try not to use the "Lei" form unless there's a sign of formality, like "signore" or something.