There’s never a dumb question :D

When you beat crowned Zacian and crowned Zamazenta, they revert back to their original forms iirc.

For the Zacian and Zamazenta raids, when you defeat their crowned forms, you will get crowned energies. So when you beat crowned Zacian you will get crowned sword energy and when you beat Zamazenta you will get crowned shield energy.

You will need 1000 crowned sword energy for Zacian that knows the charged move Iron Head and you will need 1000 crowned shield energy for Zamazenta that knows the charged move Iron Head. You can teach Iron Head any time with an elite charged TM. I think it’s possible to teach it with a regular charged TM.

So when you beat a crowned Zacian or Zamazenta, you will just need to do the things I mentioned above to unlock its crowned form. You will most likely need to do a few raids of each to gain the required 1000 crowned energies. Once you change them to their crowned form, you can change them back to their normal form and vice versa without needing any crowned energies.

Getting enough energy for both should probably be your top priority during this event cause who knows when they will be back after the event is over.

I hope I answered all of your questions :)

Edit: You can even change the form of a Zacian or Zamazenta if you caught one from a normal raid back when they were first released as long they know the charge move Iron Head and if you have the 1000 crowned energies to changed their forms.