As I understand it, Z-Wave is substantially more closed/proprietary. Both Thread and Zigbee are protocols that run on top of 802.15.4, which Espressif already has in other products.
I think Z-Wave is a bit more open now but everything I’m seeing indicates Zigbee has pretty thoroughly killed it by not requiring arduous certification processes and being generally easier to work with. Z-Wave is technically superior with the ability to have devices directly communicate with each other for basic functionality but at least for me that wasn’t worth the massive markup and I’m slowly replacing anything z-wave with Zigbee equivalents.
Zigbee supports binding, allowing devices to directly control each other without the intervention of a controller. For example, I've Inovelli light switches that communicate directly with Zigbee smart bulbs.
Z-Wave is completely different from Zigbee. Different frequency bands, modulation, etc.
And there are still just two suppliers of Z-Wave radios, as far as I know. I haven't bothered to re-check recently. Up until ~2022 there was just _one_ supplier, you could open any Z-Wave device and find exactly the same chip. Sometimes on a cute little daughter board.