In Russian this sounds like "I am an engineer from the factory." Zawod means factory in Russian.
Yes, I just gave that as my translation and was marked correct. This usage (by trade, or by profession) is falling out of use, though - I don't think I've ever heard anyone use it except in a book or TV show set in the past.
When this sentence is spoken can you really hear the first Z or does it sort of merge with zawodu?
"ze" is rather before clusters of consonants that would make it hard to pronounce, here you just pronounce it as double "z".
Does English's "by profession" have any more meaning to the sentence when added? The same with "z zawodu" and Dutch's "van beroep".
Yes. If we talk about an actor instead of an engineer, for example, then it does add to the meaning.
"I am an actor." Every waiter and bartender in Los Angeles is an actor.
"I am an actor by profession." Now, if he's telling the truth, then he makes a living with acting. He doesn't have to wait tables or tend bar.
Yes. I'm a Computer Scientist by training, but a teacher by profession.
But doesn't it mean "a calling"? I think that translates to "z powołania".
I may be an engineer by profession but I may hate it, right?
In my personal understanding as a native English speaker, Vocation and Profession are identical words. I personally think the sentence is awkward with "by profession." I don't usually hear this expression. I hear "as a profession," maybe. I hear "professional" if it proceeds certain jobs/vocations/professions. But, I do believe the words are as perfect of synonyms as synonyms can be. ;-) Maybe I'm wrong, but I don't ever think of a calling that someone loves when I hear vocation. In fact, I never even connected the word with "vocative" or "voice" before this particular discussion. Hah. For me, it's just a word for a profession.