零 is seen not earlier than in seal script.¹ It consists of “rain” 雨 and “command” 令, the latter lending its sound. The original meaning may have been “light rain,” with “small” and “zero; nil” as extended meanings.² 令 was originally a depiction of a kneeling person receiving a command.³
Unicode has created a different character 零 to allow for hard coding a different style. However, it is still the same graph. Often displaying 零 with a different font will be enough to show the different style as well. See resources below for details on the differences in style.