I'm not sure if there's enough information to make this something that people will want to hack at for very long. It's probably not a standard substitution, as three of your words start with "ff", and it's uncommon in English to have a duplicated 1st letter for a word. It's also probably not a reordering, since uncommon letters like 'z' keep showing up, and common letters like r, s, and t aren't used once.
However, the word length looks quite plausible-- no plethoras of long words or really short ones. So my guess is it's a non-standard substitution.
Might help if there was more to go on, but maybe not. Depends, I suppose. Tell you what-- you solve mine and I'll work some more on yours:
NfgC FFn, XkG uCRBuLaN gedKrb QmBK ebj! Kj dMGdBo, PmBK ebj EK fBF cneLaN yLa ImhT rMcDehT bpdJ LkG bmBFd kBNGb lL. fblC UkG hBFlgC Pmd bFKBlFlRlGb mDPDsaJ lcPhLtL ahPapNB sNk IDIsN pcSo HhPapNB, kL fGoBM af mJdgI FCnPaF gkEDeN.