People are often puzzled as to how to distinguish between ‘posao’ and ‘zanimanje’ in English. The easiest way is to refer to everything as ‘job’. But English has much more to offer.
A job (countable noun) is a regular activity you perform in exchange for payment, especially when you work for a company or public organisation. For example: ‘A friend of mine told me his last job was with a computer firm and his current job is in advertising. But, he would like a job in TV. Are there any jobs (not work or works) in TV? He might apply for a job there. It might be hard to get a job (or land a job) there or even hold down a job (keep a job) because of so much competition.’
Work (uncountable noun) is used in a more general way to talk about activities you do to earn money, either working for a company or as a self-employed individual. For example: ‘This friend of mine started work when he was 18. More people are in work (have a job) in Croatia today than 10 years ago. However, lots of people are still out of work (without a job). They are looking for work, but they have difficulties finding work. Another friend of mine is returning to work after being on maternity leave for a year.’ It is worth remembering that when asking someone about their job, you should ask ‘What do you do (for a living)?’ Also, be aware that when you are busy you have a lot of work to do, not a lot of job.