Try (a=1..26, shift +13 mod 26):
Check “zfnels” — ROT13 back? That would be “msaryf” — not English. “zuxe” ROT13 → “mhkr”. ttbyq msaryf mhkr
t → g t → g b → o y → l q → d space m → z s → f a → n r → e y → l f → s space m → z h → u k → x r → e Try (a=1