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Marcus Rashford and Joshua Zirkzee both scored twice to ensure the Portuguese continued his unbeaten start to life at Old Trafford.

Rashford scored the first goal of the Amorim era last weekend and opened the scoring again here, netting after 34 minutes before adding his second shortly after the second half kicked off.

Zirkzee followed suit, clinically slotting his two efforts into the back of the net for his first goals since the opening day of the season.

United moved up to ninth on 19 points, while Everton remaind in 15th, two points above the relegation zone.

Despite the margin of victory, though, Amorim believed the performance was "up and down like a rollercoaster".

"The result was good but we were pragmatic. It was not pretty but we were pragmatic. We did our job, which is to win," he said.

"You can feel that we have a long way to go. You can feel that in the first few minutes, when we were OK, but then Everton controlled the game. Then we got the goals in the right moment and that changed the game.

"You can't just focus on the result, you have to focus on the way the result appeared. Like before the game, we have so much to do, but it is better to work with victories. Let's focus on the performance more than the result.

"You can feel it during the game. It isn't a line of top performances, it is a rollercoaster of performances.

"We have some moments when we are good, but then we have moments when we have to suffer. We did it again, like in the Europa League. We need time to train and improve. It is better to work with victories."

For Everton, it has now failed to score a goal in each of its past four Premier League matches, its most recent goal coming on 27 October (AEDT) against Fulham.

It was also the fifth time Everton has lost a Premier League match by a margin of four goals or more under manager Sean Dyche, with the Toffees only losing more such matches under David Moyes (seven).

The Everton boss lamented his side's individual mistakes at Old Trafford, insisting it must improve ahead of facing fellow struggler Wolverhampton Wanderers this week.

"Early in the season there were too many mistakes and that was the same today. In the first 32 minutes I thought we looked a good outfit, we looked progressive," Dyche said.

"We played well and opened them up. One mistake led to another mistake, and before you know it you're 2-0 down and then a third one straight after kick-off and that is my biggest gripe. It goes to show if you don't stay tuned in all the time it doesn't work for you and that was the case today.

"We've eradicated some mistakes from the start of the season. It is very difficult when you make such glaring individual mistakes. It is a very difficult task.

"This has to get parked quickly. I don't expect our team to make so many mistakes again. They are well versed in this scenario, it has been here for three or four years at this club.

"We are trying to break this pattern of work for a breakthrough, drop down, breakthrough, drop down. That is the next challenge by reacting in the next game. Every game is a big game, it is true for Everton."