Does zero-lift angle of attack depend on Reynolds number?
The aerodynamic coefficients  $c_l,c_d,c_m$ are in general functions of the angle of attack $\alpha$, Reynolds $Re$ and Mach number $Ma$. For your experiments, since you are operating in a very low $Re$ regime, assuming incompressible flow, your lift, drag, moment curves will largely depend on viscous phenomena (i.e. $Re$ number). Generally, as $Re$ number drops, the boundary layer thickens. For this reason, you will expect a lower $c_l$ number (due to viscous decambering) and a higher $c_d$.

You may also discover non-linear behaviors even on operating angles due to laminar separation bubble forming/bursting on the suction surface and this is very dependent on the turbulent intensity of your wind tunnel so the stall angles and post-stall behavior may not be the same for flight conditions where turbulent intensity is very low.

Finally, you can confirm with Xfoil that for $Re=300k \Rightarrow \alpha_{L=0}=-4.33\ deg$ while for $Re=150k \Rightarrow \alpha_{L=0}=-3.64\ deg$ for the NACA4412.