Half-life of $W$ and $Z$ bosons $W$ and $Z$ bosons should decay through weak interaction. But their half-life is around $\tau = 10^{-25} s$ which is a typical value for particles decaying through strong force (instead of a $10^{-12}-10^{-6} s$ for a weak interaction decaying particle).
Why this can be?
 A: Yes, it is 

correct to say that the W boson is decaying through weak interaction despite its very small lifetime.

The weak interactions were dubbed such in the last century because, at low energies compared to the mass of the W, about 80GeV, the large mass of this particle appeared squared in the propagator of this virtual particle in all weak process amplitudes. This is summarized in the Fermi constant G of the relevant amplitudes. Thus, weak decay widths involve the square of G. 
As a result, virtually by dimensional analysis, e.g., μ decay must be of order ${\cal O} (m_\mu^5 /m_W^4)$! Recall the mass of the μ is ~ 0.1GeV, so a thousand times smaller than that of the W. (It is a 2-scale problem: the electron and neutrinos' masses are negligible here.) So, all low-energy weak processes are "cursed" by such a suppression. 
As you probably covered/will cover in your particles physics course, the actual small width for μ decay giving it its long, microsecond, lifetime, is
$$
\Gamma_\mu \sim \frac {G^2 m_\mu ^5}{192 \pi^3}=\frac{g^4 m_\mu^5}{m_W^4 \pi^3 ~6144},
$$
where g is the usual EW coupling.
Now, contrast this with the real W decay into μ ν, where there is no propagator suppression:
$$
\Gamma_{W\to \mu\nu} \sim g^2 m_W /48\pi , 
$$ 
whose order you find again by dimensional analysis: it has to be $m_W$, as it is a one-scale problem---all other scales are negligible.
The ratio of the two, then, amounts to 
$$
\frac{m_\mu^5}{m_W^5} ~ \frac{g^2}{128\pi^2}
$$
and so 20 orders of magnitude. And you thought these leaps only happen in astronomy...
You may also marvel at the power of the SM electroweak unification which leads you to such  sensible descriptions across 20 orders of magnitude.
A: Both are weak decay processes but the intermediate vector boson decay occurs at very much higher energies of 80-90  GeV compared to 1 GeV for beta decay.
