4th Problem (hint)

Station X,

7th September 1941,

Dear Mister Thompson,

We have intercepted several messages from
35° 33’ North, 21° 11 East. They have the same
indicator (CORSO). We think they are in depth.

Please, decipher them ! Your colleague, Mister Tutte
will be able to re-build the key after that!

These are the messages (without any indicator) :

1) ZRZVW POFZM CMPJX UQUNH MZQVF PSRVH ZJBEC XRTXX

2) KXXLI MDPPB HXMSV QIZZR BZHRB JUFGW WPHIP LAXXX

3) MQPYE ZOLZF WYWHA UZIPS RQKIA VJUEN YNCCR OEYRL

4) XHTOC DKGRS YENJL UVYPX FNTED QBYIJ SYPDB OEXXX

5) JRGSD BKVDQ NEAQA HBIZD SKUEN LMEMF TRPIR XXXXX

6) UXXSE ZOEVS URSRV YXEZL LFYRA ZGLVB CPBXX