We report on the magnetic, thermodynamic, and electronic properties of the Gd-doped Kondo-lattice compound ${\mathrm{YbFe}}_{2}{\mathrm{Zn}}_{20}$ (${T}_{K}\ensuremath{\approx}32$ K) by means of $T$-dependent magnetization, specific heat, and electron spin resonance (ESR) measurements. As Gd is incorporated in this system (${\mathrm{Yb}}_{1\ensuremath{-}x}{\mathrm{Gd}}_{x}{\mathrm{Fe}}_{2}{\mathrm{Zn}}_{20}$), the Yb contribution to the Sommerfeld coefficient remains almost unaltered for $x$ = 0.005 and 0.01 at ${\ensuremath{\gamma}}_{\mathrm{eff}}\ensuremath{\approx}$ 500 mJ ${\mathrm{mol}}^{\ensuremath{-}1}$ ${\mathrm{K}}^{\ensuremath{-}2}$, however, for $x=0.05$, it is reduced to ${\ensuremath{\gamma}}_{\mathrm{eff}}=450$ mJ ${\mathrm{mol}}^{\ensuremath{-}1}$ ${\mathrm{K}}^{\ensuremath{-}2}$. As expected for heavy-fermion systems, the ${\mathrm{Gd}}^{3+}$ ESR experiments show an enhanced Korringa relaxation rate, $b=d(\mathrm{\ensuremath{\Delta}}H)/(dT)$, due to the exchange interaction between the ${\mathrm{Gd}}^{3+}$ localized magnetic moment and the high $4f$-conduction electrons ($ce$) density of states at the Fermi level. Below ${T}_{K}$, the ${\mathrm{Gd}}^{3+}$ ESR $g$ shift presents a peculiar $T$ dependence. For $x\ensuremath{\lesssim}0.01$, we associate the $g$ shift to an internal molecular AFM field due to the $ce$ screening of the ${\mathrm{Yb}}^{3+}$ magnetic moments in the Kondo condensate with a value of $\ensuremath{\lambda}=\ensuremath{-}2.80(1)$ mol Oe/emu. The negative value reflects a singlet nonmagnetic ground-state formation, consistent with a Kondo-lattice system. Still below ${T}_{K}$, but for $x=0.05$, the ${\mathrm{Gd}}^{3+}$ ESR $g$ shift presents a positive $T$ dependence, which we now associate to an internal molecular FM field due to a ${\mathrm{Gd}}^{3+}\ensuremath{-}{\mathrm{Gd}}^{3+}$ superexchangelike interaction via extended Fe $3d$ $ce$. A Fermi surface reconstruction process is found to take place in the crossover from the high-$T$ to low-$T$ regimes, such that a momentum transfer dependence of the ${\mathrm{Gd}}^{3+}\ensuremath{-}ce$ exchange interaction $[{J}_{f\ensuremath{-}ce}(q)]$ in the former is lost as the Kondo condensate sets in.