mine sounded better though.
as far as i'm concerned, zajebać means either to steal something, or to kill [somebody/something]. jebać and zajebać are two different things. if somebody said to you 'ja cię zajebię', you'd better run, fast. you're in for... a beating!
(if it's between friends tho, it's very similar to 'i'll kill you!' in a jokey manner)(when some thug grabs you and says that, it's very bad...)