Worm is crawling on the wall - Elrond, Angius - you could do opportunity attack with a weapon you are holding.
Zombie tries to attack bellow with disadvantage.
But Bellow is more than ready to escape
Please do opportunity attacks and next turn - either in one post or separate as you wish
Rolls
Zombie slam to hit - (1d20+3)
(5) + 3 = 8
Zombie slam to hit disadvantage - (1d20+3)
(4) + 3 = 7
damage - (1d6+1)
(1) + 1 = 2