Is this a parallel sentence? If so how can it be written more simpler.

The space shuttle was both a marvel and huge.

The space shuttle was huge and marvelous.

The problem with the original sentence is that it's trying to use a noun and an adjective to describe the space shuttle. To make it parallel, you need to make both descriptors nouns ... or both adjectives, as I've done above.

The space shuttle was both a marvel and huge.

Yes, the given sentence is an example of a parallel sentence because it uses the "both...and" construction.

To simplify the sentence, we can remove the unnecessary repetition and make it more concise. Here's a simpler version:

"The space shuttle was huge and marvelous."

In this revised sentence, we have eliminated the word "both" and rearranged the order of the adjectives "huge" and "marvelous" to make it more straightforward.