There are various synonyms for the phrase "more difficult" that can help to add variety and depth to your writing. Some possible options include "challenging," "arduous," "tough," "problematic," "daunting," "complicated," "complex," "demanding," "trying," "formidable," "onerous," "onerous," "troublesome," and "exacting." Each of these words conveys a slightly different nuance or emphasis, allowing the writer to convey a more precise and nuanced message. By diversifying your vocabulary and using synonyms, you can make your writing more engaging, expressive, and memorable.