Complex sentence: Xenophon's "De Vectigabalus" probably exaggerates his methods, but for instance a law making it difficult to use public money for minor military operations ensured that a surplus was available for public works.
Split into simpler sentences: Xenophon's "De Vectigabalus" probably exaggerates the impact of his methods. However, he did introduce a law making it difficult to use public money for minor military operations, which ensured that a surplus was available for public works.