That's completely normal at the first step of the language transformation. Actually it's required if you do a file by file transformation first while wanting to maintain interface compatibility.
I'm not sure I would take this kind of path, I would much more focus on refactoring the project to small and easily translatable components with small boundaries, but it's cheap to try things.
https://github.com/oven-sh/bun/compare/claude/phase-a-port#d...
that isn't particularly surprising, but the point is I would expect getting things more stable than the zig version would take a bit.