4 neutral wires bundled, two smart switches, how to pair neutrals
Bundled together sounds like the USA so you can run a neutral from each switch and connect them to the existing four neutrals with a red wire nut,if it's 14 AWG. A better way would be to install a neutral, white, wire from the first switch to the second switch and then from the second switch to the bundle of neutrals since you have an in and out for neutrals on each switch, provided that in and out are not backstabs but back screw clamps.