Teaching with Moodle

You can get the result with with "meta link" course strategy (standard moodle to propagate inscription) 

https://docs.moodle.org/en/Course_meta_link

For instance:

Course A Content :
- Topic B
-- Course D with only content Page X (exactly the same page as in Course B) meta link access
-- Page Y

Course B Content : 
-Topic C
-- Course D with only content Page X (exactly the same page as in Course A)  meta link access
-- Page Z

or with 1 or 2 plugins , but they are no longer avalaible in community version on .org  (lack of time) 

with meta course strategy (standard moodle to propagate inscription) same as said before

+ plugin page_format (optionnal but optimal in course présentation)  

+ plugin course_ascendant/course_descendant (to organize easy navigation for students)