Who each tool is really for
Odoo
Odoo is generally chosen by companies whose software problem is operational. Inventory, purchasing, manufacturing, invoicing and field service sit alongside sales, and the appeal is running them on one platform with the option to host it yourself. It suits businesses with technical capacity or a trusted implementation partner, and with genuinely broad requirements.
Zoho
Zoho is generally chosen by companies whose software problem starts with customers rather than with stock. The CRM is a mature front-office product, and adjacent applications are available without leaving the vendor. It suits teams that want to configure rather than develop, and that would rather not think about servers at all.