He did play with the Sedins. Even one of them said that he is the best scorer that he's ever played with. They played on the same line, but not throughout the whole season, but often played onthe top PP unit. You don't think he had superior linemates compared to Zacha?
Hmm let me see for the most part you have Boeser playing with the Sedins, Peterson, Horvat and JT Miller thorughout his whole career. Did Boeser play with the Sedins all the time? No. But they were a line at times and he spent a lot of the time on the first #PP with them. That is a fact. Then you have Zacha who for the most part played with a mix of Bratt, Gusev, Nico, Vesey, Zajac, Merkley, Simmonds Stafford and Wood and barely got any PP time up until the end of the the year before last. I would say that the linemates are clearly superior on the offense. If you think that those players are on the same level playing field you are either ignorant or delusional and literally making those players I mentioned on Vancouver to be not as good as they actually are in order to claim that Boeser isn't playing with better linemates. Lets also put together the fact that Boeser also has argubaly the best puck moving defenseman in the league to assist in getting him the puck while you have Zacha normally not having the top offensive D even on his team on the ice when he is. When you have the likes of PK and Will Butcher bringing the puck up the ice you aren't geting the chances either.
A path to 50 goals for Brock Boeser - Vancouver Is Awesome Article referencing the Sedins and Boeser together.
Why Brock Boeser didn't get as many goals in 2019-20 - Vancouver Is Awesome Here is another article stating that one of the reasons why his numbers dropped was becasue of the absence of the Sedins.
Autographed Vancouver Canucks Daniel Sedin, Henrik Lundqvist & Brock Boeser Fanatics Authentic 16" x 20" Spotlight Photograph You can buy that and ask yourself why the three of them are autographed in a picture together. Maybe because they were a line?