It's an XY-Wing, but the pivot also has to be Z. That's the whole idea — if XY-Wing is new to you, read that one first, since everything here builds directly on it.
What is an XYZ-Wing?
An XYZ-Wing uses a pivot cell with exactly three candidates {X, Y, Z} and two neighbours it can see: one holding {X, Z}, the other holding {Y, Z}.
Whichever way the pivot resolves, one of the three cells ends up as Z: if the pivot is X, the first neighbour must be Z; if it's Y, the second must be; and if it's Z, it's Z itself. Any cell that sees all three cells can never be Z.
A worked example
Here's the exact board the app uses for its own XYZ-Wing lesson:
Singles do almost all of the work on this one:
Once they stall, the pivot is sitting in the bottom-right corner. It has three candidates, 2, 6, and 9; one neighbour in its column holds {6, 9}, and one neighbour in its row holds {2, 9}:
Blue & violet: the cells the logic runs on · Rose: where the elimination lands
However the pivot resolves — 2, 6, or 9 — one of the three cells always ends up a 9. R9C7 sits in the pivot's row and shares the pivot's box with R8C9, so it sees all three and loses its own candidate 9.
How to spot one
- Find a cell with exactly three candidates that sees two bi-value cells.
- Check that both bi-value cells' digits are drawn from the pivot's three, and that they share exactly one digit (Z) between them.
- Check the cells that see the pivot and both neighbours — usually in the box they share — and eliminate Z.
Practice this on a real board
Sudoku Mentoring names the technique on your board, highlights the exact cells, and gives you a guided practice puzzle. Free to start, no ads, offline.