They did state they were in 1080p, which is video mode and there should be a red dot in middle right side of screen - marked most probably 1x. Touch that button and then you can select 2 or 4x in 1080p. You can also bring up a scroller wheel to select anything in between 1x - 4x. I like the scroller wheel better, as I rarely use 4x, but going between 1x -3x helps in many video's to get close while I further out from obstacles.
If you don't have the red dot in right side of screen - don't know what to tell you other than maybe removing FlyApp and reinstalling it. Zoom has been available since about 1.4.0; so if you are at that rev on firmware - it should be there. If not at 1.4.0 - then you have to update by going to DJI website if you have Android. If Apple, they still host the updates on their Playstore.