massively cleaned up my phase 2 problem 9 solution, and made 2 dzaima/APL variations (which output the would-be arguments to ⌹ as there's no ⌹ in dzaima/APL) - one which generates the expected coefficient matrix, and one which generates a bigger one to avoid all loopiness:
https://dzaima.github.io/paste/#0ZZHBattAEIbv@xRzs4SVKH6AgPscpYettFsPXUlGu6oMxqW04LomWxzi0kLpJVAIvTaBkEsPfZLMk3RWG/tSgWBn@f@Zb/@pAGi94/@SPn8xtYXRXLpZ7pq8al6iUadu4UbCgIZ2EFbnj5ebEe0vaH9L@90I2O9/gFHa5bozRdtVeYuvZg4qaV9b0cf@FW22POAZHL/g6tVRKXqMIP53L/kwzrP@PyHWpVoomx1qWTVd7YSO1l7COPpPJgfjE9LBKeR8kGqcLvUKepzS9hr6QSqNiTKYNxYdNr…