There are essentially two ways to approve a document in Zahara, either from the website or from a link set in an approval email.
If you are finding the approval process to be slow when approving from an email link, then it’s likely being caused by an email security filtering system such as Mimecast. These systems work by inspecting links before they get to the user as well as by checking the website once a user has clicked on a link within an email. The system will typically load the intended site in its own sandbox environment, inspect the entire page for any malicious code and when it’s done, redirect the user to the intended page. All the user will see is a loading page while this all happens in the background. If you are finding your approvals take too long to process, then ask your IT team to Whitelist (or bypass) Zahara from the filtering system entirely.
Mimecast have an article on how to achieve this here.