No. It's literally marketed as a collab, (feat. Zedd), thus it is not a solo track. She might be the only one with vocals on the track but it doesn't matter.
No. In that case, Starving is a solo, but clearly it took off because of Zedd's name and not Hailee's. Same goes for any other DJ song. They help the song sell. A solo is a song with only ONE artist in the title who sells the song by themselves with their own name.
technically, Yes. How would the casual listener hear this on the radio and think, "Oh! this is Zedd!" ?? come on now. It was a collab but not in the "She always needs a feature for a hit!1" type of way that ATRL assumes
Food for thought; this was basically the same situation as Justin Bieber's "Beauty And A Beat". Both songs were co-produced by Max Martin and Zedd, yet for whatever reason Zedd was credited as a featured artist on Break Free, yet not BAAB. Aside from the fact that BAAB was a genuine collab with Nicki Minaj, it makes no logical sense why Zedd, who contributed just as much to BAAB as he did to Break Free, is credited as a featured artist on one yet not the other. It's not even as if Zedd wrote/produced Break Free all by himself, like Calvin did We Found Love. That's an example you could argue where the DJ deserves their featured artist credit. Whereas Zedd's credit on Break Free has always seemed a little... odd. He's basically just a co-producer, like Max Martin, and he never gets credited as a featured artist. Hmm.
This song features Zedd. He is credited. It means this song isn't solo, it's a collaboration. Same with We Found Love.
Why deny it? Do you think producers don't do **** while singers who don't even write their songs like Ariana and Rihanna do all the job?