Condensation of an expression There is an expression: $(h+2p)^2(x+2y)^2 - 3p^2(x+2y)^2-3y^2(h+2p)^2+9p^2y^2$
Is there a way to simplify this to the form $l^2 + 4lk + k^2$? I tried to substitute $l = (h+2p)(x+2y)$ and $k= 3py$ and this takes care of the expressions at the two ends, but the expressions in the middle are stumping me.
Alternatively, one may try expressing it in the form $(l+2k)^2 - 3lk$, but I am unable to do this as well. However, I suspect that there is some relationship as $-3lk$ bears resemblance to $- 3p^2(x+2y)^2-3y^2(h+2p)^2$ if you factor out the $-3$. Is it possible to use Fibonnacci Identity in this endeavor?
EDIT: The original expression is $(h^2 + 4ph + p^2)(x^2 + 4xy + y^2)$ 
I converted this to $$((h+2p)^2-3p^2)((x+2y)^2-3y^2)$$
EDIT: I tried an alternative approach. I multiplied out this expression:
$$(h^2 + 4ph + p^2)(x^2 + 4xy + y^2)$$
and got the following:
$$h^2x^2 + p^2x^2 + h^2y^2 + p^2y^2 + 4hpx^2 + 4xyh^2 + 4xyp^2 +4hpy^2 + 16hpxy$$
(I'm leaving out some steps) This can be factored into :
$$(hx + py)^2+4(px+hy)(hx+py)+(px+hy)^2 +12hpxy$$
This would have been perfect except for the pesky $12hpxy$.

Question: Simplify the expression $(h^2 + 4hp + p^2)(x^2 + 4xy + y^2)$ in the form of $l^2 + 4lk + k^2$.
Working Out
Note that $l^2 + 4lk + k^2 = (l + 2k)^2 - 3k^2$.
Simplify expression to:
$$((h + 2p)^2 - 3p^2)((x + 2y)^2 - 3y^2)$$
Then expand using FOIL:
$$(h+2p)^2(x+2y)^2 - 3y^2(h+2p)^2 - 3p^2(x+2y)^2 + 9p^2y^2$$
Then define $a=h+2p$ and $b=x+2y$, and simplify:
$$(ab)^2 - 3(y^2a^2 + p^2b^2 - 3p^2y^2)$$
This form is very similar to $(l + 2k)^2 - 3k^2$
So,
$$(ab)^2 = (l+2k)^2$$
$$k^2 = y^2a^2 + p^2b^2 - 3p^2y^2$$
Simplify to:
$$k = \sqrt {y^2a^2 + p^2b^2 - 3p^2y^2}$$
$$l = ab - 2(\sqrt {y^2a^2 + p^2b^2 - 3p^2y^2})$$
Sub $a=h+2p$ and $b=x+2y$,
$$\therefore k = \sqrt {y^2(h+2p)^2 + p^2(x+2y)^2 - 3p^2y^2}$$
$$\therefore l = (h+2p)(x+2y) - 2(\sqrt {y^2(h+2p)^2 + p^2(x+2y)^2 - 3p^2y^2})$$
