Integrate Thread Motion Detector connected to border router?

Can I integrate a thread motion detector which is connected to a border router (EERO6) into my C7 to control a zwave light switch?

Not at this time. The Hubitat platform doesn't support Matter (yet).

Only indirectly.

If you are using an iPhone and you use homebridge to control your Hubitat devices via your iphone, then assuming your Motion detector is set to appear in iOS Home, you can control the switch using an automation on the iOS Home side. You could also do it using a virtual switch on Hubitat that is bridged to the iOS side - turn the switch On when motion is detected, and Off when it stops. The virtual switch can then trigger rules on the Hubitat side.

Of course, the "best" solution is to have Matter integration into Hubitat, but Hubitat has only vaguely said they plan to support Matter, but no timeline.