Verified answer

Neither is really correct but both can be understood...

The latter is really awkward, though, because it uses an English word that's just written in Hangeul.

Anyway, the authentic way to say it, I think, is "부활절을 축하합니다." which literally means "We congratulate Easter."

Yes, they both means the same, the problem here is:

행복한 means Happy, and is wrote in the own language (korean), and

also 해피 means Happy, but is wrote in english!