How can I implement an '&' inside a \left( \right) environment?

I've been running into a strange issue. I'm doing some derivations in LaTeX document, and am using the align environment to do so. Some derivations require multi-line brackets, for which I try to use

\left( \right. \\
\left. \right)


However, when I want to align my equations with something inside these brackets, I run into errors. Example:

\begin{align}
blablabla x=y \left(5 + 3 & + \right. \\
& \left. + 1 + 9 + 7 \right)
\end{align}


This runs into trouble, while

\begin{align}
blablabla & \left(5 + 3 + \right. \\
& \left. + 1 + 9 + 7 \right)
\end{align}


works just fine. Hence, I strongly suspect that the problem is caused by the first ampersand being inside the \left( ... \right) environment. Is there any way to get this to work? Any help would be much appreciated.

EDIT: For clarity: I'm looking for a way around the ampersand problem: I would like to have the ampersand inside my \left( ... \right) environment. Is there any way to do this?

A simplified version of your code:

\begin{align}
x = y \left(5 + 3 & + 1\right.
\end{align}


I strongly suspect that the problem is caused by the ampersand being inside the \left( ... \right. [construct]. ... Is there any way to get this to work?

Why? A \left ... \right pair creates a so-called "math-inner" item. What's inside a math-inner item is, well, not "visible" to the outside world. In particular, the & character cannot be "seen" by the align environment. Since such code cannot be made to work, LaTeX is programmed to throw an error message and stop.
x = y \left(5 + 3 \right. & \left. + 1\right)

The upshot? Don't overuse left and right! Fortunately, sizing large parentheses manually is not that difficult to accomplish.