Zemo’s plan isn’t as convoluted as people have criticized it for being. It’s not one of those crazy villain schemes that relies on a zillion things falling into place in a way that looks like what the heroes wanted but turn out to be all part of the master plan.
He wants the files on Bucky killing Tony’s parents, so he can use that the break up the team (specifically cap/Tony). He tries to get what he needs in the simplest way possible first, torturing the colonel hydra agent. That doesn’t work, so he moves on to framing Bucky to capture him and infiltrate for the interrogation. Not that crazy or complicated in this world. You could complain about the logistics of actually being in the right place at the right time for that once Bucky’s captured, but everyone’s all over the world in a matter of hours in this film; that’s not really a silly villain scheme, just playing fast and loose with the speed at which he can pull that together. EMP bomb to knock out power and get to Bucky unsupervised, and he has what he wants: the information on the Winter Soldier facility to go get the files on that mission himself.
Once he gets there, he exposes the frame job on Bucky to make certain he gets some Avengers there to actually reveal the truth to about Bucky’s involvement. Mission accomplished.
Several things break in Zemo’s favor that he couldn’t control, sure. But they’re just coincidences that increase the drama, they’re not anything his plan relied on; he didn’t need preternatural prediction of his enemies moves three moves ahead for things to work. It’s not a Skyfall/Dark Knight situation.
If he’d gotten the colonel to break, he’d have what he needed right away. Once he goes with plan B (for Bucky), he heads to Siberia and just needs to get someone there for the revreal; it’s good for the movie that it’s Tony, Steve, and Bucky, but the plan would’ve basically worked no matter who showed up as long as he could get the secret out.
As far as I can tell, Zemo isn’t responsible for Brock’s suicide mission at the start where Wanda gets blamed and the Sokovia Accords are brought into the mix, and again, that’s good for the drama of the movie that the team’s relationships are put under that additional strain, but again, Zemo’s plan relies on none of that.
So I don’t know who was upset about that, I skipped several pages of discussion, but Zemo’s plans are simple enough and believable within the larger context of the film.