The diagonal of Lambda is sorted. The corresponding eigenfunctions
or monomials are in this order:

u^0*v^0

u^0*v^1
u^1*v^0

u^0*v^2
u^1*v^1
u^2*v^0

u^0*v^3
u^1*v^2
u^2*v^1
u^3*v^0

u^1*v^3
u^2*v^2
u^3*v^1

u^2*v^3
u^3*v^2

u^3*v^3
