Well you have asked two different questions here.
Who are the two messengers?
Is the True Lord and the messenger of the covenant the same entity?
The verse in Malachi 3:1 mentions 3 different beings.
There is the 1st messenger who clears up the way which in the first century. This was John the Baptizer who prepared the Jewish people for the coming of the Christ.
Then we have two more entities,namely, the True Lord and the Messenger of the covenant.
These two are not the same individual according to our understanding.
“The true Lord” is Jehovah God, while the “messenger of the covenant” is Jesus Christ.
As you no doubt well know the word angel means messenger. As you are also aware we teach that in his prehuman existence and post resurrection heavenly existence God’s Son is known by the name Michael. More info
The term Archangel means chief angel or messenger. Thus it is fitting that the messenger of the covenant would be none other than God’s Son.
The temple belongs to Jehovah as the verse makes clear:
suddenly there will come to His temple the [true] Lord,
That is person (1)in the sentence.
Then the verse goes on:
and the messenger of the covenant in whom you are delighting.
This is person 2 in the sentence.
The messenger is the one sent forth to cleanse the temple and as John 13:16 says:
I tell you the truth, slaves are not greater than their master. Nor is the messenger more important than the one who sends the message.
And who sends the message?
Malachi 3:1 concludes:
Jehovah of armies has said.
The initial fulfillment of the prophecy took place when Jesus cleansed the temple. (Mark 11:15-17)
Here is where our doctrine conflicts with the premise of your question.
In the view of those who believe that Jesus is God Almighty the verse is held out as proof that Jesus as the messenger of the covenant and the true Lord who comes to his temple are the same entity since it was Jesus who cleansed the temple, driving out the money changers etc...
However the true Lord (YHWH) himself said that no one could see him and yet live.
Jesus was seen by many as he cleansed the temple of the riffraff.
These people did not die.
Still it was the will of the true Lord YHWH that was carried out on that day.
Jehovah came to His temple representatively or by proxy. Jesus (the messenger) came on YHWH’s behalf.
So question 1) the two messengers are John the Baptist and Jesus Christ.
Question 2) the Messenger of the covenant and The True Lord are not the same being.
An official source provides further details.