I've kept two Regals long term.
First was a
Red Sea Regal that I lost after a year in my system. My H.magnifica anemone wandered into a powerhead and shredded its tentacles, releasing nematocysts all through the tank. Killed all the fish except the clowns.
Located a blue chested Indo/Pacific Regal from Vanuatu the next month on Diver's Den and purchased it. Had it for 7.5 years before selling it to a local reefer because I was downsizing tanks.
Here is a picture of it from March of last year:
In my experiance, Regal's are not smart fish.
It took both of mine about a year to get fully acclimated to being in my tank and begin eating aggressively.
QT where you can monitor them for disease and get them acclimated to eating in captivity is huge in their success.
I had Tomini tangs in with both of them, and a tiny purple (the size of a quarter with fins extended, the Regal was about 3 inches long at that time) in with the second one. Other fish which are not aggressive and are not shy eaters will "show" Regal angels and other timid fish what is "food" in captivity.
Once they get the hang of it, they become fairly hardy eaters and are willing to wade in and fight for their share of the food. Initially, my second Regal was bullied by a small virgate rabbit fish.....pretty much the most meek and cowardly fish I've ever kept....I wound up removing the rabbit and the Regal got more comfortable as time went on.
Did not have any issues with them eating zoas initially. The Indo/Pacific (Blue Chest) Regal suddenly decided at the 3.5 year mark that zoas and clams were on the menu....I figured this out after a very expensive frag of Spiderman Zoa's disappeared roughly 60 seconds after introducing them to my tank.
I was no longer able to keep clams or zoas in the tank after that.
It didnt bother anything else in the tank and would eat flake, pellets, nori, steamed brocolli, uncooked scallop and shrimp as well, mysis, mysids, pretty much whatever I put in the tank.
I started with mysis and scallop which I tore into thin strips. Scallop smells strongly and it's rare that a fish wont at least go after it. I've heard of people trying little neck clams on the half shell before, but I never tried that because I didnt want to "teach" my fish that clams were a food source. Didnt work out that way....but that was the goal.
Try rubberbanding strips of scallop and nori to a rock....angels like to pick/nibble. If your dither fish know how to eat from a nori clip, try that too.....it will "teach" the Regal that much faster. It will also help if the dither fish is happy eating from the water column.....if you can get the Regal eating anything at all, odds are much better you will be able to get it onto other food sources as time goes on.