IF you mean small caliber then yes you can side graft or veneer graft. I haven’t tried a z-graft for scions that are larger than the rootstock and I get the feeling that avocado is a little more finicky than other trees. In general, side or veneer grafts are my favorite types of graft. You just want to be sure your rootstock is in an active growth phase or else it may just sit there until it fails.
K