Puzzle 15

Okay, it has been a while, but here is a new cryptographic puzzle:

HZ ZHZCECCZ LCXCZEF EUI, A WDAWR WITTAZMI GZHE UAL LCZE EI A THSHEADF JDHLIZ NID A WDHTC EPCF MHMZ'E WITTHE.

EPCLC TCZ JDITJESF CLWAJCM NDIT A TAVHTGT LCWGDHEF LEIWRAMC EI EPC SIL AZOCSCL GZMCDODIGZM.

EIMAF, LEHSS UAZECM YF EPC OIXCDZTCZE, EPCF LGDXHXC AL LISMHCDL IN NIDEGZC.

HN FIG PAXC A JDIYSCT. HN ZI-IZC CSLC WAZ PCSJ. AZM HN FIG WAZ NHZM EPCT.

TAFYC FIG WAZ PHDC: EPC A ECAT.

It is a fairly easy one, especially if you begin to recognise the quote. Enjoy!

The solution will appear in one week.

An additional puzzle: How was the ciphering alphabet formed?