4x4: Meyer, K4 and Z4

Reduction and Yau dominate the 4x4, but solvers who use Roux or ZZ on the 3x3 have methods that keep their style, and K4 avoids reduction's parity step by solving the last layer with commutators. All three are niche; they are here for completeness and for what they show about the puzzle.

Richard Meyer's method is Roux on the 4x4: two opposite centres, a block on the left as Roux's first block (three layers deep), the remaining centres, the edges the blocks did not use, then a Roux finish (the second block, CMLL and the last edges), with the 4x4's parities fixed along the way. A later variant builds a block on the right before pairing the last edges, so more of the edges can be seen.

Thom Barlow's K4 solves two centres, a block, the other centres and the first three layers without rotations, leaning on commutators; then the last layer's corners in one algorithm and its edges in up to three looks, where commutators also absorb what would be parity in reduction.

Conrad Rider's Z4 is ZZ on the 4x4: the centres, then the dedges paired and oriented (parity included), so the first two layers need no F or B turns, ZZ's F2L, the corners with COLL, and the last layer's edges with their parity.