Apple - Does iPhone X support Display Zoom?

No

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

https://twitter.com/reneritchie/status/925709868425793542

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.