They should get along ok except that the Zebra? Danios will be a bit disruptive with their frenetic swimming. I think Danios are better in a 30 inch long tank.
I think mollies get too big for your tank & as usedtobe said, danios are too hyper. I would only keep male livebearers, females will come "pregnant" (gravid) & female guppies aren't even pretty to me.
With platys you can choose different colors (they're all the same species), but again get males or your tank can become overcrowded fast. It sounds fun to have fry but gets old quickly or depressing when some fry are eaten.
Will you eventually want any bottom fish like cory cats?