# Can I say that two different quantities are zero? [duplicate]

I started to learn basics of physics in a university. I know that it is wrong to compare for example pressure and length, like $2\mbox{ Pa}\ne 2\mbox{ m}$. But from algebra I know that $0=0\cdot 2\mbox{ Pa}=0\cdot 2\mbox{ m}$. So if I have the situation that I can choose the zero levels of pressure and height at certain area $A$, am I allowed to write $p_A=h_A=0$?

For example: The equation for the pressure in a fluid of uniform density is of the form $p_2-p_1=-\rho g(y_2-y_1)$. If we choose $p_1=y_1=0$, we get the equation $p_2=-\rho gy_2$.