The Perfect Zigzag

The dance line must zigzag: up, down, up, down — every step changes direction, no repeats in a row. 💃

You get at least 2 nums with no equal neighbors. Print zigzag if the direction flips at every step (it may start going either up or down), otherwise no zigzag.

Example:

Input: nums = [1, 5, 2, 6, 3] Output: zigzag

The direction flips every step — up (1→5), down (5→2), up (2→6), down (6→3) — never repeating.