I'm playing GemCraft - Frostborn Wrath and I try to get all achievements. There is a achievement called “Derangement - Decrease the range of a gem” which I try to get. I don't know how to zoom gems to increase or decrease the range of an gem. There are now information about this in the user guide or hotkey list.
You can easily change the range of an gem by focusing the gem with the mouse. Than use the mousewheele to increase or decrease the range of the gem. In this way you can control the gem range and also get the achievement:
Derangement - Decrease the range of a gem