Gnome Shell and Unity (3D) via Compiz offer to zoom into the desktop.
Is there something similar for Unity 2D please?
Have you tried the "Compiz Configuration Settings Manager"? My guess is that even though it's 2d it's still Unity. (The following comment says you can't so that guess is likely wrong) Other than that, I know gmome-tweak lets you scale up fonts...but that's not exactly zoom. Oh! If you type "Universal Access" into the dash you should be able to use that to set zoom functions out-of-the-box with out any additional software.