Java regex to parse two levels of structure [duplicate]

I am trying to parse two levels of structure in a string. The input can of form.
x1:x2:x3::y1:y2:y3 --> where there can be more chaining with ::

The regex should be able to parse the string through :: in the first go, and then each group through :.
Output should look like:
x1, x2, x3 and y1, y2, y3

I have been able to figure out parsing one level by capturing the group.

(^[a-zA-Z\d]+):([a-zA-Z\d]+):([a-zA-Z\d]+$)

How do we make it work for two levels of parsing?

On the lighter note, would you prefer just using Split to make it simpler? I prefer regex as it has cleaner checks on data organization.