In most cases, yes, you could do that.
But the more you split up the zones, the more likely you are to short-cycle the boiler on zone calls.
To get a handle on this, measure up the existing radiation zone by zone on the current zones, and the radiation per zone after the split, and compare that to the DOE output BTUs of the boiler. If the boiler is a modulating boiler, compare it to the DOE output at it's minimum firing rate. If the amount of heat emitted by the zone radiation is less than the lowest BTU output of the boiler it's going to cycle, and if the zone emittance is a lot less than the boiler it's going to short-cycle itself into lower efficiency, higher maintenance, and shorter lifespan.
Some of the napkin-math analysis on that can be found on
this bit o' bloggery using a modulating-condensing boiler example, but the math is the same for fixed-output boilers.
