isSame produces incorrect results when DST ended in local zone but haven't ended yet in the desired timezone

**Describe the bug**

I'm having an issue when two exactly the same dates are sometimes not the same when compared using the `isSame` function.

Those dates are in different timezone (`America/New_York`) than the local timezone (`Europe/Bratislava`).

What's weird is that the the `isSame` function produces correct results on dates when both timezones are in standard time, but it produces incorrect results when Europe is already on summer time, but US is still on standard time.

**Minimal reproducible example**

In Node.js 14:

```js
const dayjs = require('dayjs')
const utc = require('dayjs/plugin/utc')
const timezone = require('dayjs/plugin/timezone')

dayjs.extend(utc)
dayjs.extend(timezone)

const test = str => {
let tz = 'America/New_York'
let day1 = dayjs(str).tz(tz)
let day2 = dayjs(str).tz(tz)
return day1.isSame(day2)
}

console.log(test('2021-03-28T00:00:00Z')) // prints "true"
console.log(test('2021-03-29T00:00:00Z')) // prints "false"
```

**Expected behavior**

```js
console.log(test('2021-03-29T00:00:00Z')) // prints "true"
```

**Information**
- Day.js Version: 1.10.4
- OS: Ubuntu 20.04
- Browser: Node.js v14.16.0 REPL
- Time zone: UTC+01:00 (Central European)

Start by locating the isSame implementation and the utc/timezone plugin entry points, then run the Node.js reproduction from the issue. Compare the two dates around the Europe/Bratislava and America/New_York DST transition; done means the 2021-03-29 example returns true while the existing behavior remains correct.

Written by the indexing model from the issue text.