SureAI

In Myar Aranath, I just killed Zoras. I did not see any kind of credit screen, so does that mean I beat the game? I went back to the Queen and Caleris in Draanas. Is there anything else left to do in the game? I am wondering because there is a lot of area on the map that is left unexplored.

No, the game doesn't have anything like that. You kill Zoras, meet the Queen (for a journal update) and Caleris (for a journal update and some rewards), and the main quest is over. There are a few sidequests to do (the Lichtbringer guild has some; the Schwarze Garde has none at the moment; Teritan in Skirngarad has a high-level fighting quest to give), but mostly the game is over. In Morrowind, after the main quest, you had much more unexplored terrain.