Yes, both ZenHub and Trello offer a Free Trial.
ZenHub is designed for Large Enterprises, Medium Business and Small Business.
Trello is designed for Individuals, Freelancers, Large Enterprises, Medium Business and Small Business.
Pricing for ZenHub Starts at $7.95/User/Month when Billed Yearly whereas for Trello Starts at $5/User/Month when Billed Yearly.
Some top alternatives to ZenHub includes Trello, Wrike, Smartsheet, Asana, Teamwork, Kanbanize, Trackboard, Zenkit Projects, Height and Worktez.
Some top alternatives to Trello includes Basecamp, Wrike, Smartsheet, Zoho Projects, monday.com, Asana, Teamwork, ProjectManager.com, Microsoft Project, Worksuite, Trackboard and Height.