Audio recording Zoom digital recorder vs CD burner

We recently did and audio recording for a customer. They wanted some redundancy so we did both the Zoom HD4N digital audio recorder and our CD burner. The CD burner gave them something they could take with them right away. The Zoom provided and uninterupted recording that we could save for them if there was an issue with the CD. We also rented them the audio mixer and a dual deck CD player. The amplification was done with 2 powered JBL  EON g2 speakers. The audio was captured by 2 wired Shure SM 58 microphones.