Is it grammatically correct to use the infinitive after the comparative adjective?

Question

For example, if I say

It is more difficult than to strip the thorns off the tragacanth.

This is likely an Arabic proverb I found in one book of Google's. It means task A is more difficult than task B. OR something is ever impossible to be done.

The translation could be understood, but what if it is grammatically not correct.

Grammarians suggest using (that, other) after the conjunction "than". Some others say "than" is either conjunction or preposition. So, if we consider it a preposition, the gerund should follow not an infinitive. Hence, my correction to the above sentence will be as follows:

It is more difficult in achieving than that of stripping tragacanth thorns.

Please review what I said.

Answer 1

In comparisons, the tense of each element has to match. For example:

It is easier to do up a zipper than to sew on a button.

This example uses the infinitive and is fine.

Your direct translation doesn't contain two comparative elements. "It" in my example is a dummy pronoun that is just there to meet the grammatical requirement of having a subject. Quoted as it is, in your direct translation of this proverb "it" could only refer to a thing you have previously mentioned - the thing you are now comparing to. If the infinitive is the tense used in the other comparative element then technically you should match it.

In your example written sentence, you have brought two comparative elements together (although you don't actually say what you are trying to "achieve" - you still refer to "it" previously mentioned) but they do not match.

It should be:

It is more difficult to achieve than to strip tragacanth thorns.

Answer 2

To get blood from a stone is easier than to get a simple answer from him.

It is easier to get blood from a stone than to get a simple answer from him.

Getting a simple answer from him is harder than getting blood from a stone.

The infinitival clause used nominally is somewhat old-fashioned compared to the participial/gerund version, but using the cleft structure gives the infinitival version a more contemporary syntax, a syntactical renovation, as it were.