The question whether the mixed phase of a gapless superconductor can support a Landau level is a celebrated problem in the context of textit{d}-wave superconductivity, with a negative answer: The scattering of the subgap excitations (massless Dirac fermions) by the vortex lattice obscures the Landau level quantization. Here we show that the same question has a positive answer for a Weyl superconductor: The chirality of the Weyl fermions protects the zeroth Landau level by means of a topological index theorem. As a result, the heat conductance parallel to the magnetic field has the universal value $G=tfrac{1}{2}g_0 Phi/Phi_0$, with $Phi$ the magnetic flux through the system, $Phi_0$ the superconducting flux quantum, and $g_0$ the thermal conductance quantum.
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