Monolayer transition steel dichalcogenide (TMD) alloys have emerged as a novel materials system for promising purposes in electronics, optoelectronics, and spintronics resulting from their tunable digital constructions, efficient lots of carriers, and valley polarization with varied alloy compositions. Though spin–orbit engineering has been extensively studied in monolayer TMD alloys, the valley Zeeman impact in these alloys nonetheless stays largely unexplored. Right here we reveal the improved valley magnetic response in Mozero.5Wzero.5Se2 alloy monolayers and Mozero.5Wzero.5Se2/WS2 heterostructures probed by magneto-photoluminescence spectroscopy. The massive g components of negatively charged excitons (trions) of Mozero.5Wzero.5Se2 have been extracted for each pure Mozero.5Wzero.5Se2 monolayers and Mozero.5Wzero.5Se2/WS2 heterostructures, that are attributed to the numerous influence of doping-induced sturdy many-body Coulomb interactions on trion emissions underneath an out-of-plane magnetic discipline. Furthermore, in contrast with the monolayer Mozero.5Wzero.5Se2, the marginally lowered valley Zeeman splitting in Mozero.5Wzero.5Se2/WS2 is a consequence of the weakened trade interplay arising from p-doping in Mozero.5Wzero.5Se2by way of interlayer cost switch between Mozero.5Wzero.5Se2 and WS2. Such interlayer cost switch additional evidences the formation of type-II band alignment, in settlement with the density purposeful concept calculations. Our findings give insights into the spin-valley and interlayer coupling results in monolayer TMD alloys and their heterostructures, that are important to develop valleytronic purposes based mostly on the rising household of TMD alloys.