What are some alternatives?
When comparing Zizozz and Slik Prospector, you can also consider the following products
Hunter - Find all the email addresses related to a domain
Clearbit Connect - Clearbit Connect is a free extension that surfaces actionable information on the people who email you.
RocketReach - RocketReach allows you to lookup email and phone for 250+ million professionals.
Email Generator - Get +50 email combinations and validate them with Rapportive
Email Hunter for Chrome - Find all the emails related to a domain with just one click
EmailMatcher - Find anyone's email address in a matter of seconds, for free