I would not recommend zebra danios for tank mates. They sometimes have a tendency to nip at long finned, slower moving fish, and they will easily outcompete a betta for food.
I would recommend harlequin rasboras, celestial pearl danios, small and peaceful tetras like neons, etc. Skunk (arcuatus) cories are a good choice as well.
Betta and guppies is almost always a bad idea IMO