Maurice Ravel - early concertos ?

[giles.enders]

Early piano concertos by Maurice Ravel;  In 1906 Ravel had the idea for a piano concerto Zazpiac-Bat to be based on Basque themes.  In1916 he had a further idea for a concerto for either piano or cello based on the novel Le grand Meaulnes.

Is it known how far he progressed with either of these projects?

[Alan Howe]

Here's a snippet about Zazpiak-Bat:

As early as 1906, he (Ravel) reported that he had begun sketching a piano concerto on Basque themes, provisionally titled Zazpiak-Bat, and in 1913 he informed his friend Igor Stravinsky that he was re-focusing his attention on it. But in late 1914 Ravel, by then installed in the south of France due to the disruptions of World War I, wrote to his student and colleague Roland-Manuel that he had to give up work on the piece since he had left his sketches behind in Paris. And that was the end of it, except that some material from the project was reworked when Ravel came to write his G-major Piano Concerto. (emphasis added)
https://nyphil.org/~/media/pdfs/program-notes/1819/Ravel-Piano-Concerto-in-G.pdf