I recently finished Etz Chaim from the Kitvei Ari (3 volumes). It took me 3 months and I want to know if this qualifies to make a siyum on during the 9 days.
This is a very nice accomplishment, and Hashem should help you finish and understand more seforim.
As far as making a siyum that would halachically permit eating meat during the nine days, it is hard for me to say that it would be permitted, and for a combination of reasons. First of all, we can only make a siyum when actually finishing what was learnt, and you write that you finished it recently. I don’t know how long ago it was finished but it cannot be more than a few days. Secondly, according to a number of authorities, a siyum is made specifically when finishing a mesechet of gemora, or a seder of mishnayos. There are opinions though that it can be made when learning a sefer of Nach but this would only be if it was learnt well with a clear understanding, together with meforshim who will explain things. Therefore, even if you did do it this way, it would still be controversial. Therefore, although this is a nice accomplishment, it is hard for me to say that it is valid it makes a valid siyum to permit eating meat during the nine days.