I want to arrange items in the following way.

Special features observed are
- Things are arranged in two columns.
- Enumeration items are arranged in two inner columns nested inside each of the two outer columns, resulting in apparently a total of four columns.
- (However, if the text is too long to put, then they do not form the inner columns. See item 5-6, 35-42.)
- Items switch horizontally between the inner columns.
How can I do with LaTeX? (For my purpose, feature number 3 above is not a must.)