Seen this a few times now, that there’s no Zoom in the Sense 5.5 camera app. Which isn’t the full truth..
There is Zoom, it’s simply hidden from the normal camera interface when you don’t use it.
So, how do I enable it? You simply pinch zoom in or out, and the zoom bar is there.
This is shown here on a HTC One with 4.3/sense 5.5.