stuck trying toZonedDateTimeISO

```
import {Temporal} from "proposal-temporal/lib/index.mjs";

...
  return (new Temporal.Instant(123)).toZonedDateTimeISO("Europe/Berlin");
// TypeError: cannot convert number to bigint

...
  return (new Temporal.Instant(BigInt(123))).toZonedDateTimeISO("Europe/Berlin");
// TypeError: use compare() or equals() to compare Temporal.ZonedDateTime
```