how did ethan and zeena disagree in the beginning of their marriage

Ethan had wanted to become an engineer. Zeena did not support his dreams.

"When they married it was agreed that, as soon as he could straighten out the difficulties resulting from Mrs. Frome's long illness, they would sell the farm and saw-mill and try their luck in a large town. Ethan's love of nature did not take the form of a taste for agriculture. He had always wanted to be an engineer, and to live in towns, where there were lectures and big libraries and "fellows doing things." A slight engineering job in Florida, put in his way during his period of study at Worcester, increased his faith in his ability as well as his eagerness to see the world; and he felt sure that, with a "smart" wife like Zeena, it would not be long before he had made himself a place in it."