This documentation is not using the current rendering mechanism and is probably outdated. The extension maintainer should switch to the new system. Details on how to use the rendering mechanism can be found here.

Integrator manual

Integrating forms using FormZ is much like a classic Extbase/Fluid integration. You will have to use regular tools: layouts, templates, partials, but also FormZ ViewHelpers.

You will still have to respect some constraints for FormZ to work correctly.