What is the main obstacle in Scott and Zelda's marriage in the book, Z: A Novel of Zelda Fitzgerald?

The main obstacle in the couple's marriage is Scott’s alcoholism, which puts a great strain on their marriage. Every time things began to get better in their marriage, Scott will once again begin drinking too heavily, and thus bring to head all of their former problems. Alcohol brings the couple financial instability, as Scott spends most of his money on drinking. Alcohol also causes some of the worst arguments that Zelda and Scott have, as Scott becomes verbally and sometimes physically abusive when he is intoxicated.