Consider solving the following system for $x$
\begin{align*}
a - b e^{\theta x} - cx = 0
\end{align*}
According to your favorite computer algebra program, one possible (and the simplest) is 
\begin{align*}
x = \frac{a}{c} - \frac{W(b \theta \exp(a\theta/c)/c)}{\theta}
\end{align*}
where $W$ is the product-log function, or Lambert $W$ function along the 0 branch. Is there an analogous solution to
\begin{align*}
\textbf{a} - \textbf{b} e^{\boldsymbol{\theta}^\intercal \textbf{x}} - \textbf{C}\textbf{x} = \textbf{0}
\end{align*}
where $\textbf{a}, \textbf{b}, \boldsymbol{\theta}, \textbf{x} \in \mathbb{R}^n$ and $\textbf{C} \in \mathbb{R}^{n\times n}$? If it helps, I'm willing to accept $\textbf{C}$ to be a diagonal matrix, therefore we have almost separate systems except for the pesky $\boldsymbol{\theta}^\intercal \mathbf{x}$.