I agree, he came back and went straight for Ethan.0
This has gone way beyond a misunderstanding into a near aiding and abetting of Ethan's criminal activities.
(Or Ethan could set up Zach as a patsy, fall guy.)
And Zach's actions - even if they are unknowing and ignorant - will help endanger more people like Val, John and Iris.
This is no longer just a falling out between two former friends.
He's not thinking about apologizing, he teams up with a guy that openly wants to hurt his "friend".
He's helping Ethan and putting people(ones that are true friends of the MC) in harms way.
If later he sees Valeria or Erynn being harmed by Ethan, or someone somehow convinces him that Ethan is the bad one...
And Zach helps bring him down... Good for him i guess, but in terms of being a friend the damage is done.
No amount of sad, apologetic, faces will make me forget that he chose to trust this Ethan piece of shit over "me", and teamed up with him to screw me and my friends over.