I can show you a RAH-66 Commanche picture and it did exist, that does not mean the US, or anyone is using them.
You can use wheels-based platform does not mean you can deploy with that, the UK uses Apache on HMS Ocean in Libya does not mean Apache was suitable to be Naval operation, you have landing gear issue, you have anti-Rust issue, you have navigational issue with land base helicopter (Land Base-Fwd Looking Radar is not suitable for Naval Operation), unless something is designed from ground up as a naval platform, you don't use them in the Navy, that's why the US Navy uses SH-60, not UH-60. I mean, sure I can park a UH-60 on a Navy Ship, that does not mean it was "being" used by the Navy.
And finally, you are using 1 single picture as a reference.......I mean, as I said, you can't even tell me what is the specification of Z-21, the only thing you actually know, is that it looks like an Apache....I mean, what type of Engine was it using? What is the MTOW? How does it store in Carrier Hanger bay, I mean, you sure do have faith on something you know literally nothing other than seeing it in a picture with a number.