Jacob's first name is Jacob. The dutch pronounciation comes close to YAHkob and stays far from the english DZJAYkob. The 'o' is closer to the 'o' in 'boring' than to the 'o' in 'come' and the k is pronounced without letting escape too much loose air.
More complications:
In Holland, Jacob's name is shortened to Jaap, which is pronounced like Yahp. It starts like the word 'Yahoo', but before the 'hoo' is pronounced, it's simple closed with a 'p', which is also pronounced without too much loose air.