I want to find the Covariance of $cW$ and $Y - cV$. Which of the following is correct?
$$\mathrm{Cov}(cW, y - cV) = c \mathrm{Cov}(W, Y) + c^2 \mathrm{Cov}(W, V)$$
$$\mathrm{or}$$
$$\mathrm{Cov}(cW, y - cV) = c \mathrm{Cov}(W, Y) - c^2 \mathrm{Cov}(W, V)$$
(I'm going to assume that $V$, $W$, and $Y$ are all random variables, and that where you wrote $Z$ you meant $Y$.)
We know that $\mathrm{cov}(X,Y) = E[XY] - E[X]E[Y]$, so in your case, $$ \begin{aligned} \mathrm{cov}(cW,Y-cV) &= E[(cW)(Y-cV)] - E[cW]E[Y-cV] \\ &= E[cWY - c^{2}WV] - E[cW]E[Y-cV] \\ &= cE[WY] - c^{2}E[WV] - cE[W]E[Y] + c^{2}E[W]E[V] \\ &= c\Big\{E[WY] - E[W]E[Y]\Big\} - c^{2} \Big\{ E[WV] - E[W]E[V] \Big\} \\ &= c \cdot \mathrm{cov}(W,Y) - c^{2} \cdot \mathrm{cov}(W,V). \end{aligned} $$