What if I don't use zap?

Ideally you want to add an option via a function or interface:

  func New(optOne bool, log func(string, ...any)) {
    if log == nil {
        log = func(m string, a ...any) { fmt.Printf(m, a...) }
    }
    log("starting; optOne=%v", optOne)
  }

Or something along those lines.