Suppose an author created a book "Learning Mandarin", which contained a bunch of readings and assignments in English and Chinese for learning the language. The problem is, they have to work with a special publisher who can publish both in the western markets and in China, so they use a Chinese textbook publisher capable of handling this.
Now suppose the same author took the basic components of that book, recycled the readings, and rebranded it as "Learning French". It resembles the content of the first considerably, but it's for a different audience that the first publisher doesn't even serve.
The author already did much work to consider the pedagogy behind the first book, so the second book will be naturally quite similar. Can this author work with a different publisher for the second book? Or because many components are reused (simply translated Chinese parts to French) does it mean the first publisher has copyright ownership over the second?
Can authors work with a different publisher for a derivative work?