I saw that Malbim on Shir HaShirim (1:2) quotes the Zohar with the name מכלתא דרשב״י. Indeed, the words he quotes are in the Zohar here. On the other hand, there is another work called מכילתא דרשב״י, which is a halachic midrash on Shemot (and only on Shemot) — however, it was only relatively recently reconstructed from citations in Midrash HaGadol.
Was it common to refer to the Zohar has מכילתא דרשב״י? Was this Malbim's misidentification of the two, or a known broader phenomenon?