How is Zack's behavior in handling insurance applications best described when evaluated against ethical guidelines?

Zack's behavior is best described as "not diligently performing his occupational duties" when evaluated against ethical guidelines. This choice indicates that Zack may be failing to execute his responsibilities to the required standard, which is crucial in the insurance field where accuracy and thoroughness in handling applications can significantly impact clients and the organization.

In the context of ethical guidelines, diligence encompasses a commitment to performing one’s work with care, attention, and a strong sense of accountability. This includes ensuring that all applications are processed accurately and that all relevant information is gathered to make informed decisions. A lack of diligence can lead to errors that may harm consumers, create financial risks for the company, or lead to regulatory penalties.

This is distinct from the other options, which suggest specific types of unethical behavior. For instance, while "lack of transparency" implies that Zack may not be forthcoming with information, it does not directly address his general performance level. Similarly, "irresponsible conduct" suggests a willful disregard for duties, and "lack of transparency" points to issues with openness and communication. In contrast, not diligently performing occupational duties encompasses a broader failure to uphold the standards expected in the role, thus making it the most fitting description of Zack's behavior in relation to ethical guidelines.