I think what is confusing everyone here is not necessarily a case of parallelism between gerunds/infinitives.
In general, you should either have gerund and gerund, or infinitive and infinitive. The problem here is you cannot
have infinitive and infinitive because it violates the idiom, enjoy verb-ing. Therefore you must have the following:
I like running through the forest more than I enjoy walking through crowds.
If you get rid of 'enjoy', then you can use either.
I like to run through the forest more I like to walk through crowds.
This sentence sounds a little bit repetitive with the double 'like'. Here is perhaps a much more succinct way:
I like running through the forest more than walking through the crowds.
We do not to repeat 'I like' because it is implied (this is called an ellipsis).
Hope that helps

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