The true irony, is that when they were still in Vaudeville, before they started doing the movies, they were 5 brothers who could play 4 roles, so if one got sick they could rotate and play each other, they were so multi-talented and so similar looking under the getups, that only one of Groucho's daughters could tell when her father and uncles weren't "themselves".
Harpo went years not speaking, because he never could speak without his accent, unless he was doing a deadpan impersonation of his brother's fecockta accents.
Mimi's boys are sorely missed, and where Lawrence Fine and the Howard Brothers can be emulated fairly well (as seen by the recent movie where the impersonations were so spot on, and the made for tv movie about their lives behind the camera, again with excellent impersonations), it is doubtful anyone could ever play Leonard (Chico), Adolph (Harpo), Julius (Groucho), Milton (Gummo), and Herbert (Zeppo)... they were classy even when playing four of the most classless guys you could ever meet.
I think you captured the "real" Zeppo more than any of their films did. He was quite a character, but was drafted into the act to replace the quieter, gentler Gummo, and never got the chance to grow into his character like his older brothers.