Matteo is doing well.. his hair is growing in on legs..

I am having a behavior issues.. my old chihuahua and my tiny 2 1/2 lbs are tormented by him I separate them but as soon as he sees them he tackles them.. he knows I don't allow it.. but he will any how sorta like a stalking game..and he don't fight them he just tackles and won't stop till I said ahhh or no.. he stops but a min later he's at it again.so I separate him.. don't know how I should handle this? Thank you..