I believe that several of us have discussed this with Jack Heuer and others who were associated with Heuer during the relevant period. The three Zodiacs that Mark shows were made by Heuer, "no ifs, ands or buts".

Here's the way I believe it went:

• In the 1960s / 70s, producing chronographs was far more difficult than producing simple watches, even the automatics. Each chronograph movement was received from the maker (say, Valjoux), but had to be adjusted and fitted, etc. This took a lot of know-how and was labor intensive.
• There were numerous watch brands in the 1960s, but relatively few companies actually producing chronographs. I have heard estimates of the Swiss companies actually making chronographs . . . around one dozen (12) / maybe 15 or 20.
• Heuer was one of these companies producing chronographs.
• So when a company like Zodiac, Dugena, Bulova or Hamilton wanted to add some chronographs to it line of watches, it would go to a company like Heuer to arrange for the production.
• These "Poor Man's" Heuers were produced by Heuer, just like the Heuer chronographs. Many of the components were identical; of course, some brands used their own designs.

: Remember that Swiss watchmaking of the period was something of a
: cottage industry, with innumerable parts suppliers feeding a
: much smaller number of manufacturers, who would be responsible
: for the final assembly into a watch.

: For some Zodiacs, it's pretty much impossible for even the most
: devout brand loyalist to deny that they were made by Heuer:

:
:

: The model references are the same, and the serial numbers fit
: perfectly into batches of Heuer-branded watches.

:
:

:
:

: For those that are less clearly derived from a Heuer, the picture
: is less clear. There was obviously an amicable relationship
: between the two companies for the watches above to exist, so
: it's no great jump to think that Heuer may have given its
: blessing for its parts suppliers to make available things like
: fluted pushers to Zodiac.