Oh dear, I guess you have cracked the two caesar cryptos...
This one is more difficult. Although a simple substitution is easily cracked...
Again the characters are limited to A-Z... But I think I can come up with a 256 version again.

Enjoy!

DX PYU THNCKYPX KWV XWA FTI OUTV PYCR NX GOCUIV C TN CNZOURRUV QUOX EUHH VWIU XWAO RWHAPCWI MUX CR UGIHDUYZYORI PYCR HCPPHU FYTHHUIKU ETR IWP PWW YTOV ETR CP