Your example shows necessity of adding a term string that spans over the statement to the left. I think it is not very difficult to implement grammatically zo'au-clause: just creating a structure like prenex, and make it elidible famyma'o of a statement.
However, zo'au-clause will produce more complex semantics than the current for the following reason:
logical items like negation, numbers and bound variables semantically span over the following items, and "postnex" should break the logical structure of the leading statement when it appears at the end of the statement.
It is not good for me, and I don't intend to implement "postnex" to la zantufa for now.
An alternative idea is to use {no'a} with SEI (or experimental _new_ SOI of la ilmentufa):
tu'e lo mabla cu fasnu .i lo zabna cu fasnu tu'u sei ca lo nu mi stuvi'e le sralygu'e cu no'a