Addressing the heavy-quark mass effects for differential observables such as the qT spectrum in the Drell-Yan process plays a key role for precise determinations of the W-boson mass at the LHC that are based on the ratio of the W-boson and Z-boson spectra. In this talk I will discuss a proper treatment of the finite charm and bottom quark mass effects in the factorization theorems for resummed qT spectrum. In particular, I will focus on the secondary mass corrections to the rapidity anomalous dimension (aka Collins-Soper kernel) and show their impact on the Z-boson spectrum at NNLL order.