Overview
========
You'll basically go through the following phases
- 4/5/6's, or D/5/F's
- polarity relations
- letter the corner boxes
- number the edge boxes
- resolve letters <-> numbers
- speedrun to finish

It's a pretty easy solve, there are always several avenues open for investigation.
Points not to miss:
- biggest+smallest = middlest+middlest in the length-4 zipper
- [DF]/[46] pairs really restrict what can go in column 9's black kropke
- The pressure is really on the numbers 3 and 8 in the bottom 3 boxes

Proof of uniqueness:
https://sigh.github.io/Interactive-Sudoku-Solver/?q=.Whisper%7E5%7ER3C1%7ER2C1%7ER1C1%7ER1C2%7ER1C3%7ER2C3%7ER3C3.Whisper%7E5%7ER1C7%7ER1C8%7ER1C9%7ER2C9%7ER3C9%7ER3C8%7ER3C7.Whisper%7E5%7ER7C9%7ER8C9%7ER9C9%7ER9C8%7ER9C7%7ER8C7%7ER7C7.Whisper%7E5%7ER9C3%7ER9C2%7ER9C1%7ER8C1%7ER7C1%7ER7C2%7ER7C3.Zipper%7ER8C3%7ER8C4%7ER8C5.Zipper%7ER7C2%7ER6C2%7ER5C2.Zipper%7ER2C2%7ER2C3%7ER2C4%7ER2C5.BlackDot%7ER5C8%7ER5C9.BlackDot%7ER5C7%7ER5C6.WhiteDot%7ER5C8%7ER5C7.WhiteDot%7ER5C6%7ER5C5.X%7ER1C4%7ER1C5.X%7ER8C6%7ER9C6.X%7ER6C3%7ER6C2.X%7ER5C9%7ER4C9