The Canada international is already the highest try-scorer in Warriors history, and he showed at Scotstoun on Friday that he'll be a potent attacking weapon in the run-in to the season.
After only seven minutes, the winger went over for a try which brought the stadium to its feet. Midway through the first half he cut in off his wing and took a great line to come on to a flat pass from Adam Hastings to carve through the Zebre defence for his second try.
He almost claimed a hat-trick late in the game, crossing with five minutes remaining only to have his score ruled out for a forward pass by Hastings.
Speaking in The Telegraph, Van der Merwe said: "It was a pity to miss out on that last try, but it probably wasn't a forward pass, the referee just didn't want to give it to me. But other than that I couldn't have asked for a better start to my comeback. There was a great crowd out there, the boys played really well and I was lucky enough to finish off a couple of them."
Van der Merwe arrived at Scotstoun two weeks ago following a clash of personalities with Dean Richards, who wanted the experienced wing, who turns 32 next month, to turn out for Newcastle Falcons' development team in midweek. Van der Merwe was allowed to move back to Glasgow but any worries that a lack of rugby may have left him less match sharp than turned out to be unfounded.
"I felt up to speed, but then I did have four games for Canada in the World Cup qualifiers in January and February, which helped a lot with game fitness," said Van der Merwe.
"I didn't feel I had to prove myself, although I think there were a lot of expectations. I just wanted to go out and enjoy my rugby and play the way I did when I left here. I had a little bit of a tough time in the last year, but now I'm back at the club I love I just want to enjoy my rugby.
"The shape of the team hasn't changed since I was here before, and the way we want to play is very similar. Some of the guys who were in the academy when I was here before are now full-time pros and starting games, but fundamentally not much has changed - there are a lot of familiar faces and everyone is just enjoying their rugby."
With the business end of the season coming up and Glasgow sitting at the top of the PRO, Van der Merwe is happy that coming back to Scotstoun has been a good move, with the focus on the present a welcome sign of a side not getting too far ahead of itself.
"From here we take every game as it comes," he added. "We've got to focus like we did here: this was Zebre and we could maybe have switched off a little bit but the way we came out and played speaks volumes about this team, where we want to be and what we want to do."