Positively once the H4 COS is approved until the EAD is approved, you are not allowed to work. However, in case you are working by mistake, and USCIS brings this issue in the future especially for your permanent resident card process, you can always look into INA 245(k) to defend your case. See memo guidance from USCIS on INA 245(k)
However note that the INA 245(k) is only a defense.
The best solution is to work with your employer to take a break until the H4 EAD is approved, and if you are confused or need help on the matter, please call (510) 7425887 for a consultation.