Welcome, Trip Aces.
I think the main problem with the likes of Zeo is that he is given nothing memorably evil to do - no killings, no big putting-the-villain's--plan-into-action scene, nothing.
We keep being told what bad news he is but seeing nothing. "I'd rather have stayed in prison than have let HIM free!!!" but what do we see him do now that this menace is let lose? Nothing that is inventively diabolical.
Campare this with the henchmen that the public do remember, Grant, Oddjob, Jaws, Onatopp. All of them are given plenty of killings and working inventively on the villain's plan things to actually be seen doing.
To make this new villain memorable he has to be seen doing stuff that is memorably villainous.