All survey responses are 100% anonymous. There is no option for administrators to be able to see who submitted responses to an engagement survey. This is by design, as it's important for employees to feel confident in giving honest answers and not fear retaliation from their employer.
While administrators can view the anonymized and aggregated responses of the survey, Zenefits prevents these results from being filtered in a way that would expose the identity of a respondent. Any filtering that would narrow the responses to less than 5 will not be permitted, in order to maintain anonymity.