There is already a work-in-progress implementation of HIP on top of OpenCL https://github.com/CHIP-SPV/chipStar and the Mesa RustiCL folks are quite interested in getting that to run on top of Vulkan.
(To be clear, HIP is about converting CUDA source code not running CUDA-compiled binaries but the Zluda project discussed in OP heavily relies on it.)
(To be clear, HIP is about converting CUDA source code not running CUDA-compiled binaries but the Zluda project discussed in OP heavily relies on it.)