VN is an "action noun"(e.g., れんしゅう [practice], べんきょう[study]). When VN is followed by the verb する, it is transformed into the verb VNする. The above two patterns have the same meaning.
はつおんを れんしゅうします。
I practice pronunciation.
はつおんの れんしゅうを します。
I practice pronunciation.