The Zeno map, as it is often called, first appeared in Venice in the year 1558 as a part of a small book that contained accounts of voyages in the North Atlantic and westward to the shores of America. The author was Nicolo Zeno, and the book purports to be a retelling of the exploits of an ancestor and his brother, during their exploration of these regions towards the close of the 14th century, or more than a century and a half before the publication of the book.
The map shows the North Atlantic and the countries bordering it, which the author claims is contemporary with the events recounted in the book. It is now known that the narrative was manufactured by the younger Zeno himself not long before the publication of the book, and the same is true of the map. So it does in no way reflect geographical knowledge in the 14th century. We now know that Zeno's principal sources were Olaus Magnus' map of the North, the Caerte van Oostland of Cornelis Anthoniszoon, and old maps of the North of the Claudius Clavus type with elements taken from southern sea charts of the 15th and 16th centuries. Zeno probably put the book and map together for the purpose of giving Venice, the author's native city, the credit for discovering America more than a century ahead of Columbus. In the bottom left hand corner we see two lands (Estotiland and Drogeo) that perhaps represent the eastern coast of America.
As for Zeno's Iceland, we need not look far to its sources, it is obviously taken from Carta Marina. The mountains, rivers and all the pictures are gone and the ice floes off the east coast on Olaus' map have become islands.
In spite of its discreditable parentage, the Zeno map was to have a remarkable career. For the next 40 years it influenced most maps that were made of Iceland.
Here is a copy of the Zeno map from a book by Henrich Peter von Eggers, Priisskrift om Grønlands Østerbygds sande Beliggenhed, from the year 1793.