Translation:I will explain everything to your friend.
Pretty much. I don't think of it so much as the "zu" being implied somehow, though, but rather as the dative case just being what carries that grammatical meaning here. The verb "erklären" takes both accusative/direct and dative/indirect objects, with the accusative/direct one being what is explained and the dative/indirect one being who it is explained to. The dative case used to mark an indirect object in this way often implies a "to" or "for" relationship, and we would definitely translate it in this sentence by adding the word "to" to the dative/indirect object in English.
Except we wouldn't say it with that word order in English. We would say: "I will explain everything to your friend." For a verb like "to give" you could say "I will give your friend everything" or "I will give everything to your friend" but for the verb "to explain" you can only use the second version. To be honest I don't know why!
This is correct, not wrong ... https://screenshots.firefox.com/EtVnmOrdw9riwLk4/www.duolingo.com
You can tell by the -em ending on deinem that deinem Freund has to be singluar dative and either masculine or neuter. Those are the only times that ein words have an -em ending.
"I shall explain all to your friend" not accepted by Duo.. Getting bored repeating "will" so used the interchangeable "shall" (in modern English), plus "all" because it's shorter and equally accurate. In spoken English, of course, it would simply be "I"ll explain". Yet again I wonder whether to persevere with the rigid inadequacy of Duobloodylingo.....
Hi. I'm not a native speaker, but there is quite a bit of freedom in word order in German. There are standard/correct forms, but then inside of that there are some choices in some circumstances. I think the direct and indirect object can be swapped sometimes. It probably effects emphasis. But a native speaker would be able to explain it better.