Does iPhone X support Display Zoom like the iPhone devices before it that are larger than the iPhone SE?
Not yet. It’s a whole new UI so my guess is that has to be redone at the second scale still. Dynamic text is there and improved, though. https://twitter.com/roelvangils/status/925696251651330050
That makes sense to me because if a developer wants to support iPhone 6 sizes and larger then they already should have support for iPhone SE which is used when Display Zoom is turned on on an iPhone 6. There is no smaller version of the iPhone X with its notch and rounded corners, thus no Display Zoom. Next year we might have display zoom on iPhone X Plus.
Updated 2020-09-18: YES, it does as of iOS 14 beta 3 (which also means iOS 14.0 and later). And it looks like apps should be updated to support that, otherwise top and bottom of the screen are not used (eg. in Twitter app).
Earlier: A quick and dirty update after the release of iPhone XS [Max] / XR: looks like Zoomed View will be supported on XS Max and XR, but not on X nor XS.
Please feel free to update with more details as they emerge.
It is not (yet) supported and there is a good reason.
An iPhone 6 in Zoom mode has a screen just like an iPhone 5. An iPhone 6+ in Zoom mode has a screen just like an iPhone 6.
An iPhone X in Zoom mode would be another new screen size, with a new size of the notch. (The notch would physically be the same size, but because of zoom mode it would be fewer pixels).
At the moment there are still many apps that support the iPhone X, but in a slightly hacked way: If the developer didn't want to switch to a newer SDK, they could check the size of the phone, and if it is iPhone X sized then the developer assumes it has an iPhone X sized notch and an iPhone X sized area for the home button at the bottom.
These developers wouldn't think of supporting iPhone X in zoom mode, so things wouldn't work. Another problem is that as long as an app runs fine on iPhone 5, it will run fine on iPhone 6 in zoom mode, so I can test on an iPhone 5 which I need to test anyway. To test iPhone X in zoom mode, I have to switch zoom mode on which is a pain because it restarts all apps.