My assumption is that, since z is decreasing over time, it would indicated:
$\frac{dz}{dt}$ is negative with units of $(\frac{m}{s})$
Gravity is positive with units of $\frac{m}{s^2}$
I am assuming the coefficients of friction are opposite of the direction of motion $\frac{m}{s}$, hence it would be negative hence both $C_l$ and $C_n$ would negative. With:
$C_l$ having units of $\frac{kg}{s}$ and $C_n$ having units of $\frac{kg}{m}$.
Are there assumptions correct? Assuming that m = kg. I believe that the units for my $C_n$ are wrong as the "sgn" is throwing me off.