How to convert multiple Next.js pages to customs domains (hosted on Vercel)

Question

I would like to redirect Next.js page to a custom domain:

Example : For the https://domainzzz.com/user/josh, Josh would like his page to be access by https://joshwebsite.io

For the https://domainzzz.com/user/bob, Bob would like his page to be access by https://fannythebeauty.co

For the https://domainzzz.com/user/yann, Yann doesn't want a custom domain so nothing changes.

How to do that on the fly (like Super.so) with Next.js and Vercel?

Thanks