I'm not talking about the magnifying glass that appears at the bottom, but I think I just figured it out. If you're browsing using media net, find a neutral part of the screen to touch, if you keep your finger there for like a second, a small icon of a globe and a magnifying glass will appear, then when you take your finger off, it'll zoom in or out. On google in landscape mode, it zooms 50 and 100%. I'm not sure if you can control the zooming. In portrait mode, it zooms at 100 and 103% for me.
if you press the magnifying glass a slider scale will appear beside it. You can adjust the zoom (+ or -) but I haven't found a reliable way to activate it yet.
Once you've zoomed, press the mag symbol again to make it disappear.