Zach Welles is an entrepreneur who founded an online app called Boogaroo and has a business based in Silicon Valley, California. He is also a Rayna Jaymes superfan.
He meets Rayna when she agrees to play a private charity event but she finds that the crowd is not so enthusiastic about country music.
He tells her that he spent his youth caring for his disabled mother and grew up listening to her records, going as far as to ask why she is not making more music. She tells him that she feels that she has nothing to say but he does not believe that.
After she returns to Nashville, he phones her to say that he's thinking of flying there to discuss working with her further. When he arrives, he meets Rayna and Deacon at the Bluebird where The Exes perform. Afterwards, he offers Rayna the chance to work together and she agrees to go into business with him after he discusses his plans for Highway 65. He also introduces her to his friend, video director Damien George who wants to direct the new video by The Exes.
He accompanies Rayna to The Exes' video shoot and when Rayna notices that Scarlett does not appear entirely happy she expresses her worries to Zach who tells her to trust Damien's vision. He also meets Will at the shoot and gives him his phone number so they can talk about his career. When they meet again backstage at Luke Wheeler's concert, he reveals that Luke is selling his label to Rayna and offers him the chance to sign with her.
After Rayna dies in a car crash, he gives Deacon a copy of a video that he had a cameraman film of Deacon and Rayna recording their concept album together and later demands the master tapes of the unfinished album. Rayna and Deacon's friends rally together to finish the album.
He began a romantic relationship with Will Lexington. He later tells Deacon that he wants Bucky gone from the label and also suggests releasing Maddie's debut single as a digital download at midnight. He brings in marketing manager Alyssa Greene to join the label and is also eager to sign singer Jessie Caine, letting it drop to Deacon that she was previously married to label boss Brad Maitland.
After Will learns from Jakob Fine that Zach likes to play around, Will discovers that Zach has two cellphones and notices a phone call from a man named Jeff. Confronting Zach, the latter says that he is an ex-boyfriend still hung up over their break-up and in order to show Will how much their relationship means to him he phones Jeff in Will's presence and tries to calm him down, telling him it is time he got over him.
He soon becomes more controlling and when Maddie is shooting a commercial and the executives want to change a lyric to her song "Saved", Deacon takes issue with the change and confronts Zach, who tells him Maddie has to do the commercial the way it is stated in the contract or else he will walk. Deacon later tells him that he is done with their branding partnership.
Still furious, Zach decides to cut off the electricity and funding to Highway 65, forcing Deacon and the artists to move. Deacon pays Zach a visit in an attempt to get through to him, which does not work. Will is not happy that Zach is doing this. Zach also gets an offer from Brad Maitland to merge Highway 65 with his own label but does not respond. Having heard what has happened, Juliette decides to take matters into her own hands and contacts Mackenzie Rhodes, who phones Zach with probing questions, thinking she will use it in an article until Juliette decides to come clean about stealing the song meant for Maddie.
Deacon finds Zach at the Highway 65 offices and realizes that he has been so controlling as he is a very lonely person and likes the feel of being in control. He gives him the offer to continue working at the label not as a dictator but as a partner, which he accepts.
By the start of Season Six he and Will Lexington have split up and he is seeing someone else. He later tells Deacon that he is leaving Highway 65 to return to California in order to make a Senate bid. Following Will's heart attack and discharge from hospital, Zach returns to Nashville and calls by to see him, also revealing that he and Mark are no longer together.
After Alannah tells Deacon about Brad's behavior towards women and his attempt to sexually assault her, Deacon contacts Zach and they confront Brad, with Zach telling him that he will sign over his record label to him. A few months later, he is seen back together with Will.