I am setting up a tankless water heater to provide hot water plus 2 zones of heat. Do I need a check valve for each zone? There already is a check valve for the entire system. Thanks for your help.

What brand and model of direct water heater are you using ?

Best Wishes

if you are using seperate circulators for each zone then you use the type with internal flow check.
example... taco 007IFC
if you are using one circulator with 2 zone valves then no check/s needed.

That makes good sense. Thanks. Since I am not using a boiler, but an on-demand, tankless system, Do I still need a flo control valve on each zone? My sense tells me 'no', since there is no possibility for 'flo' unless there is demand for heat or hot water. Am I correct? Thanks.

when one zone calls for heat, the hot water will circulate by gravity thru the other zone. so the zone calling for heat will get nice and hot while the other zone will get either warm or very hot depending on the piping layout.
so, use the circulators with the internal flow check. some places sell them for the same price as the regular circulators.