Tip: here's a quick way to zoom

Mercury-4 has the handy Focus  option in its tool bar, but you can also quickly zoom in on any part of Mercury-4's interface by holding down the Ctrl key or Cmd key and clicking on the area you want to zoom into.  Repeating the same action will zoom back out.

Note: it doesn't work on the keyboard keys, so click just outside of them to zoom into that area.