No Macross Zero is a prequel to SDF Macross. Also it is Overtechnology not robotechnology.
The ASS-1 crashed in 1999. This prompted reengineering of its technology and reorganization of the UN as a world government because of proof of the existence of extraterestrials. Some nations and groups did not want a world government, viewing it as world domination, this lead to the creation of the Anti-UN alliance. The so called Unification War or UN War began.
By 2007 the Anti-UN was already defeated. The Anti-UN we saw in Macross Zero, in 2008 a year before SDF-Macross, are little more than a very well funded mercenary terrorist group. Since Overtechnology was deseminated around the world the technology for the variable fighters and destroids being developed were copied.
Indeed in SDF Macross we already saw the UN and Anti-UN fight with Overtechnology conventional arms with the UN Forces F203 Dragon II fighter and Anti-UN forces MiM-31 Karyovin fighter. The former piloted also by Roy Focker.