I am sorry to ask a question that obviously is a sum of separate questions about a process: Should the decay rate of Z0 be related to the decay of the "higgs" composite field it is eating? And, should this composite field, being a pseudoscalar, decay at the same rate of the neutral pion? But I hope that people will be able then to give at least partial answers.
It is a fact, surely so trivial that it is rarely mentioned, that the pseudoscalar neutrals have about the same electroweak decay rate, simply scaled by the cube of its mass. Just as the charged mesons scale by the quintic of its mass, a case which is more popular in textbook exercises. Time ago the particle data group provided the table of decay rates and masses for all the particles, and then I drew this plot. Surely some point has moved slightly by now, but you can see the blue line, cubic, where all the neutrals align to scale, and the green quintic power for the charged particles, whose decay is ruled by the Fermi mass, and then a lot slower than the neutrals.
You can see how the blue line touches the neutral pion in the left part of the plot and the Z0 in the right part. Yes, the muon and tau are also there, as they also decay via the electroweak interaction.
(EDIT: current pdg numbers are off two sigma. More precisely we have for Z0: 2495.2/91187.6^3 = 3.291*10^-12 and for the neutral pion, using only indirect measurement: (6.58211928*10^-22/(8.30*10^-17))/134.9766^3 = 3.225*10^-12. Given that the pion lifetime has a huge error (it is 8.30 \pm 0.19), the discrepancy is still within one-sigma, but it goes up to almost 3 sigmas if we include the only direct measurement of the decay, ATHERTON 1985)
So, can this be interpreted as slight evidence of, or arguments for, technicolour?