Ethics of Spinoza - Question about Translation

Question

Spinoza, Ethics, De Dei, Propositio 15, Scholium:

Si igitur ipsi ex suo hoc absurdo concludere tamen volunt substantiam extensam debere esse finitam, nihil aliud hercle faciunt quam si quis ex eo quod finxit circulum quadrati proprietates habere, concludit circulum non habere centrum ex quo omnes ad circumferentiam ductæ lineae sunt aequales

I understand the meaning of the sentence but I can not realize the literal meaning of the bolded part because of faciunt and si.

In short Spinoza already explains that some authors conclude from an absurd proposition (A) that the extended substance must only be finite. He demonstrates absurdity of A and hence he deduced that the finiteness of the extended substance is not necessary. Here he says that if those authors persist in believing in A and conclude from it that the extended substance must be finite, they are like one who supposed a circle to have the properties of a square, and then concludes from this that the distance of the points on circumference from the centre of the circle is not equal.

Answer 1

Literally, '...they do nothing different than if someone... (makes the other conclusion about a circle)'

Or, to translate a bit more loosely, '...what they do is no different than what some other person does if he/she... (makes the other conclusion)'

Or '...they act no differently than if some other person... (makes the other conclusion)'

The adjective alius/alia/aliud can be treated as a comparative, and quam can introduce the second term in the comparison. That second term can be either a single word or phrase, or (as here) a whole clause.