English approximations are, in some cases, very loose, especially for vowels. They are intended to give only a general idea of the pronunciation. See Czech phonology for a more thorough look at the sounds.
^[dz] occurs only in loanwords and as an allophone of /ts/ before voiced consonants. The word podzim is usually pronounced with [dz], but a careful speaker would pronounce the two letters separately.
Dankovičová, Jana (1999), "Czech", Handbook of the International Phonetic Association: A guide to the use of the International Phonetic Alphabet, Cambridge: Cambridge University Press, pp. 70–74, ISBN0-521-65236-7