Is zooming in the browser the same as zooming on a mobile device?

Question

When I press Ctrl+ in a modern browser, the page zooms, including images; a similar effect is apparent when pinching and zooming on a mobile device. Everything on the page scales proportionally.

My question is, when the browser zooms and when the mobile device zooms are they doing the same thing internally? I'm specifically interested in the relationship of physical pixels with display pixels with device-independent pixels. This is a domain that can become rapidly convoluted when considering media queries and the like.

Edit: I've got some good answers, my appreciated. I was hoping to find out how they differ from a technical point of view. i.e. "one is scaling x, the other scales y". Any insight here?

Answer 1

In my observations, no, they are not the same. When I pinch-zoom on my mobile device it zooms in without affecting the relative page size. When I Ctrl-+ on a PC, the page is adjusted to fit in the same screen pixels width, which alters flows to fit content in fewer "virtual" pixels.

EDIT: There is also a difference between mobile pinch-zoom and mobile double-tap-zoom. I have observed that double-tap-zoom does affect the flow of the page, while pinching does not.

Regarding "CSS pixels", isn't it apparent from how elements with sizes defined in px units are affected? It would seem that "CSS pixels" remain how they were intended at 100%/