It is not enough for the following word to start with two consonants and there are plenty of counterexamples, e.g. 'z brzegu', 'z krzewów', 'z prądem' (herbatka :D), etc.
'ze' is used in one of the following situations (from http://sjp.pwn.pl/poradnia/haslo/ze-i-z;12186.html ):
If the following words begins with a pair of consonants the first one being z,s,ż,sz,ź,ś,z' or s' (though I must admit that I'm not sure what the apostrophe means here...)
(the case relevant here) Before the forms of pronoun 'ja' : 'ze mnie', 'ze mną'
In front of some words which have to be learned as exceptions (e.g. 'ze Lwowa', 'ze łzami w oczach')
This is very helpful thank you! As for the "s'" I believe that it stands for the "soft" or "palatized" form of s. It's not something that is notated in writing, but is something that can be heard in speech and pronunciation. To my knowledge it stands for the way "s" is pronounced when the middle part of the lounge is close to the roof on the mouth, or the hard palate. I might be wrong though, but I remember reading this somewhere. Thanks again for the information!
Hey guys, Currently in Poland and these topics came up in class today :) the pronoun changes depending on how difficult it is to fluently pronounce the words together. Yes you will find it happens most with letters like z,s,ż,sz,ź,ś,z' or s' because they are similar to Z but there are exceptions. Also depending on the difficulty of pronunciations you will find it with other words like mnie :) Other examples of this with different prepositions are W poniedzałek W czwartek WE WTOREK notice again here how the prepositions without e would trigger a repetition of the letter W, which in turn would cause a lot of confusion. You can find the same patter within English articles for example An apple would be A Apple which isn't very clear. Oh interesting fact sometimes this process in the language causes a glitch, for example: 'An Apron' the original english name for this item was Napron or A Napron, over time due to confusion the N transferred over to the article and voila 'An Apron' Hope this helps :)