It would be understood but it should have the second 'to'. Generally, you need to use to with both infinitives when they're before and after a comparative. To finish early is better than to finish late. To take a computer apart is easier than to put it together. Or you could use a dummy pronoun: It's better to finish early than finish late. It's easier taking a computer apart than putting it together, Or you could use nouns (gerunds): Finishing early is better than finishing late. Taking apart a computer is easier than putting it together. You could also mix verbs and nouns: To take a computer apart is much easier than putting it together.

Yes you do need another "to". Let me explain why. You are making a comparison between two nouns: "NOUN1 is easier than NOUN2". "Put it together" is not a noun. That is why your sentence is incorrect. To make your sentence work, you need to transform the idea of "put it together" into a noun. "Put" is a verb, not a noun. There are two magic ways that work to change any verb into a noun: (1) the infinitive, and (2) the present participle. "To put" and "putting" are both nouns. (They are also other things too, such as adjectives, but that doesn't concern us here.). Hence there are two ways to fix your sentence: (1) "To take apart a computer is much easier than to put it together" (2) "To take apart a computer is much easier than putting it together"

As far as I'm concerned : ) To take apart a computer is much easier than (to) put it together == It's much easier to take apart a computer than to put it together. The rule: [ Sometimes, the infinitive can serve as a formal subject in English. To utilize "to" behind "than" in your sentence can make its components all noticeable and highlight the comparison between both infinitives. ]

To take apart a computer is much easier than putTING it together (again). Is how to say it naturally. (again is optional) To take apart a computer is much easier than to put it together.

"To take apart a computer is much easier than put it together" "To take apart a computer is much easier than putting it together" "To take apart a computer is much easier than to put it together" all correct