Convert from zoll [Switzerland] to gnat's eye

Unit Definition (zoll [Switzerland])
In Switzerland, it is now considered a metric unit equal to exactly 3 centimeters (1.1811 inches). There's no change in the plural.

Unit Definition (gnat's eye)
The gnat's eye is an idiomatic "unit" of distance; it's common to hear that something is "as small as a gnat's eye". In fact, the eyes of typical gnats tend to have diameters similar in size to a hair's breadth: roughly 100-150 micrometers (0.10-0.15 millimeters).