Title:The Great Catsby

solve this puzzle by finding the real letter of each words

PS GPN AIBM
QDJ OMSN EMS
DSO QPJIN XOEM
DSO HMSZ IPUM
EKZGN DEKSQ DSO
ZGM XGDERDQSM DSO
ZGM MZDJN


BTW the O and D might be switched
Hints
D=A​