As I am watching the replay, I thought that I would take notes on anything I see that looks seriously suspicious.
The first thing that I noticed is that the barcodes scouting with the overlords is dreadful and they are not even bothering to check whether you expanded. Even with the opening pool first from you, and the attack you commit to, your opponent does not care about scouting to see whether you expanded or if you are sending more units across the map. They are just blindly droning up, and this is a correct call because you are, in fact, not getting more aggressive. This does look suspicious but at 4.2k MMR it's hard to read too much into this because maybe it is just a massive mistake by your opponent.
At the 3:10 mark, your opponent does do something that I think is very weird. You have an overlord at the side of your opponents natural, they do not have any vision of it, and it's an uncommon position, and despite this, your opponent sends his queen over to where the overlord is to prevent it from being able to get vision.
As the game progressed the complete lack of scouting was very odd (they did not even have overlords rallied around the edges of their base; all the overlords were rallied to the dead space in between the natural and main: people are usually not this incompetent at this mmr).
After he killed your third and your evos with the attack and he backed off, I think that the movement of his roach army very much mirrored your movement, even though he had zero ideas as to where your army was. Also, your opponent began to look at the exact position your army was stationed to, in my opinion, check it out and see whether he could take it on.
Then we come to that last fight and the sniping of the creep tumours. I think that this move, right here, is the final nail in the coffin and is the last shred evidence we need to say that this player was a map hacker. I feel very confident to say that your opponent is not that good at the game, and is nowhere near the level where you can guess the exact location of creep tumours, especially when the creep tumours are not perfectly spaced out. And since your potato of an opponent managed to do something that Serral would find near impossible, I think that is very fair to say that your opponent is, first of, really bad at the game and that they are very clearly hacking (and their hacks allow them to play at this MMR).