Digby's new friend

Kitty-corner, or should I say doggy-corner, from our house is Zephyr's house. He's a black lab whose a big galoomp and friendly. Digby took to him right away and whimpers when the Big Z is outside on his porch. I have no great clue as to why Digby likes some dogs right away and others not so much. He does seem to have a preference for black dogs, as well as old and infirmed ones (not a threat). Susie, of course, is fine with the whole setup, because she likes just about everybody.