The Gemara, based on Rava’s statement that Rav Shizbi misled Rav Chisda, concludes that putting everything into one tallis and taking out is considered hatazala and thus mutar according to everyone.
If we turn back to 19b, we see that there were two talmidim who disagreed -- one saved with one kli and one saved with many. The Gemara says this is the machlokes in our sugya of Rabba bar Zavda and Rav Huna. The simple interpretation would seem to be as Tosfos explains there that the talmid that saved many keilim was saving to the same chatzer (Rabba bar Zavda) and the one saving only one, was following Rav Huna that even to same chatzer you can only save one.
Based on this, Tosfos on 19b challenges Rashi’s interpretation of the sugya there as Rashi says that the talmid who carried many keilim did it by folding them up together and carrying out all in one shot. But as we said above, this is what our gemara said everyone calls matzil! The Ramban (and Maggid Mishne says Rambam learned this way as well in 23:23), explains that according to Rashi there is a difference between a real mixture where everything is poured together and mixed, as opposed to where all the keilim are put in one tallis and carried out but not really mixed. This latter case is not considered Matzil and only allowed according to Rabba Bar Zavda.