Do "play immediately" cards in the zombie turn affect the number of cards a zombie player will have in his hand?
When playing as the zombie, you first fill your hand of cards (4 cards if there is 1 zombie player, 2 cards if there are 2 zombie players). After drawing all cards, you then decide in which order you would like to resolve all of the "play immediately" cards just drawn. After resolving these cards, they are not replaced.