If you mean,

(3x^2)(e^(6x-10x-3)) + (6x)(e^(3x^2-5x^2-3x+6-52))


3x^2 e^(6x-10x-3) + 6x e^(3x^2-5x^2-3x+6-52)

(which both say the same whereas your version opens more brackets than it closes - latex would reject it - did it?)

... then, re-read this bit...

you'll have as your derivative e to that same (complicated) power but the whole thing then multiplied ...
(... by the derivative of the power.)

By the way, why not collect like terms in the power (and its deriv.) - but this is by the way.