Your personal Tumblr library awaits
Parts of Coruscant, especially in the extra-dense areas, don't have any cooking implements in the apartments besides a microwave and small fridge. (Hot plates are a fire hazard.) Instead of cooking for themselves, residents visit food vendors or buy microwave meals. Prepackaged snacks that don't require refrigeration are also common.
You know those 'microwave hacks' and 'MRE hacks' and 'prison food hacks?' That's the kind of "cooking" that Kallus knows.
In contrast, Zeb learned how to cook both at home and at school, and had an abundance of fresh food to work with. Lasan's dominant government put out standardized cookbooks of healthy, easy to make meals for the home ec classes. These standard meals often vary, changed to match regional tastes, in individual schools.
The Wookies, being close allies and intellectual partners with Lasan, have these cookbooks saved as part of their Lasani Remembrance Archives. Alderaan also made a habit of trying to preserve at-risk cultures, and had copies in their own archives.
There's a big part of the holonet devoted to saving old recipes and adapting them to new circumstances--the Lasani diaspora is just one of many peoples trying to cope with being away from 'home.'
Zeb looks for Lasani recipes and subsitutions for Lasani spices, of course, but he also searches for recipes from Ryloth, Mandalore, and--the hardest to find--the Jedi Temple. When a Spectre is feeling particularly down, Zeb will make them something from their home to cheer them up.