Complex Scroll Interaction Issue with three scrolls: horizontal UIPageViewController, vertical UIScrollView, and horizontal UIScrollView on the top of them

Hello Apple Developers,

Here is an interesting and quite challenging problem. It is a real problem in our product Drinkit (https://apps.apple.com/app/id1495622004) that we can't solve elegantly. There are three scrolls: a horizontal UIPageViewController, inside each page there is a vertical and paginated UIScrollView, and on top of all this, there is a horizontal UIScrollView with tabs to manage the UIPageViewController.

We want to make the vertical scroll on these tabs forward to the view controller on the current page of the UIPageViewController so that the page in the vertical UIScrollView scrolls accordingly.

I have created a prototype to reproduce this situation. https://github.com/zsergey/Scrollviews

Thank you for your help!