There should be no problem. Zetafax and Max (any version) don't "integrate" as such. Zetafax appears as a printer, and if you put at the top of your fax something like
%%sendfax:{faxnumber}%%
Then Max puts the fax number field in {faxnumber} during merge, and Zetafax takes the whole string and then puts fires it out.
The syntax above is probably not right, but its correct in principle ;-)
- Pasta