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!

KL QJZ NPVGBJQL BOW LOE TNA RZNW QJGU VL SRGZAW G NV GVIRZUUZW CZRL YZPP WOAZ LOER UOPEQGOA FZL GU ARRNRBKKROKJ QJGU PGQQPZ TJNPPZABZ YNU AOQ QOO JNRW YNU GQ