VoiceOver navigates from top-left to bottom-right, irrespective of the view hierarchy. This is usually how content is arranged in left-to-right languages since sighted individuals tend to scan the screen in an “F-shaped pattern”. VoiceOver users will expect to navigate the same way as typical users. Predictability and consistency are very important to accessibility. Please refrain from making customizations that “improve” on default behavior (eg. ordering the tab bar first in the swipe order). That said, if you have received feedback that the order of elements in your app is surprising, there are a couple of ways you can improve the experience.
If VoiceOver should read a view’s subviews one after the next but is not, you may need to hint to VoiceOver that the elements contained within a single view are related. You can do this by setting
myView.shouldGroupAccessibilityChildren = YES;
To support complex navigation structures that span multiple containers or include interfaces rendered without UIKit, consider implementing the container protocol on the parent view.