EzZoom

Well, there's not a lot to say, press the zoom key ('Z') to zoom in.
For easy handling this does also decrease your mouse sensitivity while zoomed in.

This mod is fully configurable, you can set how strong the zoom is,
and you can change how much your mouse sensitivity gets affected. Additionally, there is a new "Advanced" Zoom feature, which allows you to zoom in steps, you can then use your mouse wheel to zoom in/out while pressing the zoom key. This feature can also be fully configured.