Z - Zip / Transpose
This atom is monadic, which means it takes one argument.
Transpose / flip a matrix; switch the rows and columns.
For a flat list, wraps it (each element becomes its own column, which means transpose then flips them all into one row). For a single value, if it's a number, error, and if it's a character, wrap it twice (because characters are internally single-character Python strings, which are iterable).