Incorrect behavior of `dayjs.tz`

**Describe the bug**
```ts
const date = new Date() // utc timezone date
// 2024-09-04T10:04:12.774Z

dayjs.tz(date, "Asia/Kolkata").toISOString()
// 2024-09-04T10:04:12.774Z

dayjs.tz(date.toISOString(), "Asia/Kolkata").toISOString()
// 2024-09-04T04:34:12.774Z
```

**Expected behavior**
```ts
dayjs.tz(date, "Asia/Kolkata").toISOString()
// 2024-09-04T04:34:12.774Z
```

**Information**
- Day.js Version: v1.11.13
- OS: macOS
- Browser: Node.js
- Time zone: UTC

Start by reproducing the two dayjs.tz examples from the issue in Node.js with the timezone set to UTC, comparing Date and ISO string inputs for Asia/Kolkata. Trace the dayjs.tz entry point and timezone handling, then verify that both inputs produce the expected 2024-09-04T04:34:12.774Z result.

Written by the indexing model from the issue text.