The classical Kirchhoff's law of thermal radiation indicates the equality of angular/spectral emissivity and absorptivity under thermal equilibrium, which basically introduces an intrinsic loss in energy harvesting and conversion processes. Recent theoretical studies have shown that multijunction solar cells can reach the Landsberg limit when using nonreciprocal semitransparent thermal absorbers, but there are still few feasible structures that can break Kirchhoff's law in semitransparent systems. Here, we propose a sandwiched nanostructure, where a dielectric layer is coated with two antiparallel-magnetism Weyl semimetals (antiparallel-MWSs) without any structural asymmetry. We demonstrate that the appearance of asymmetric high-Q quasi-bound states in the continuum (quasi-BICs) near zero-index frequency contributes to largely breaking the equivalence of absorptivity and emissivity at the same angle and frequency (|α(ω,θ)-α(ω,-θ)|~0.5) around 3.3 µm without external stimulus. We also show that the nonreciprocal properties can be tailored over a wider angular range by tailoring the thickness of both dielectric interlayer and MWS layers. The revealed mechanism and tunability in designing semitransparent nonreciprocal thermal absorbers will stimulate more comprehensive studies in nonreciprocal thermal photonics, which also show potential in next-generation magnet-free nonreciprocal energy devices.