We're talking about compiler, right? Sorry don't see why classes would be a bad match to compiling Zig code to LLVM representation. As long as we don't do lot of numbers crunching (where Fortran, R, Julia, MatLab shine), then structs/classes are ok.
Zig operates at a low level where it cares about things like manual memory-management. Compiling it to target the JVM instead of webassembly (assuming that's what you're suggesting) would be a really rough abstraction, because the JVM is higher-level. Webassembly is designed to accommodate lower-level languages adjacent to C that manage their own memory, etc
And that's not even mentioning the fact that (it sounds like) Zig's compiler already has an LLVM back-end, which means they get wasm support "for free"
