Spoiler warning: This is actually a pretty fun problem to solve, and I such I recommend trying to work it out yourself before consulting this document. For starters, I recommend reading up on how to write a single quine and trying it out yourself. Then, I recommend trying to write a quine relay with two languages by hand -- and from there, you can try writing one with three languages. This is the process by which I started getting an idea of how I would write a quine relay generator for an arbitrary number of languages.
To be added: description of how it works