  We investigate the magnetic and electronic properties of the Gd$T_2$Zn$_{20}$
($T$ = Fe and Co) compounds using X-ray resonant magnetic scattering (XRMS),
X-ray absorption near-edge structure (XANES) and X-ray magnetic circular
dichroism (XMCD) techniques. The XRMS measurements reveal that the
GdCo$_2$Zn$_{20}$ compound has a commensurate antiferromagnetic spin structure
with a magnetic propagation vector $\vec{\tau}$ =
$(\frac{1}{2},\frac{1}{2},\frac{1}{2})$ below the N\'eel temperature ($T_N
\sim$ 5.7 K). Only the Gd ions carry a magnetic moment forming an
antiferromagnetic structure with magnetic representation $\Gamma_6$. For the
ferromagnetic GdFe$_2$Zn$_{20}$ compound, an extensive investigation was
performed at low temperature and under magnetic field using XANES and XMCD
techniques. A strong XMCD signal of about 12.5 $\%$ and 9.7 $\%$ is observed
below the Curie temperature ($T_C \sim$ 85 K) at the Gd-$L_2$ and $L_3$ edges,
respectively. In addition, a small magnetic signal of about 0.06 $\%$ of the
jump is recorded at the Zn $K$-edge suggesting that the Zn 4$p$ states are spin
polarized by the Gd 5$d$ extended orbitals.
