After some months of working, Zylva finally have achieved my main expectations and is ready to be tested by those who find it interesting.
During the journey, I had to learn and relearn a lot of things. I have changed the complete structure and redefined the classes more times than I would like. I completely underestimated the job that an application could take. I thought about surrendering various times. But I persevered, and it was worth it: I'm quite happy with the result, I gained a lot of experience in Java and in the OOP paradigm, and I think it's a great first Java project.
I really hope someone finds it useful.
Open to improvements, suggestions and contributions,
Iñaki.