A new update for YouTube has brought pinch-to-zoom as an option for those with an Essential Phone. The update can be downloaded directly from the Google Play Store and comes in at version 13.34.50.
Pinch to zoom RSS
If you were irked by the inability to zoom into videos on your handset with an 18:9 display, YouTube's latest update to its streaming app, offers this solution. The update is version 12.44.