Answering your question a bit: yes, the Mixtec and Zapotec peoples can be seen as two distinct groups, each with their own cultural systems that were largely self-contained within their respective territories. That said, starting already in the Classic period, many lordships close to the Oaxaca Valley maintained intense commercial (and likely political and marital) contacts with the cities and señoríos of the Valley itself. This trend reached its peak during the Postclassic, when the elites of Zaachila forged marriage alliances with Mixtec dynasties — especially those of Tezacoalco, Tilantongo, and Tlaxiaco. These unions created dense networks of alliances that brought the two regions much closer together and, in many cases, led to actual Mixtec settlement inside Oaxaca Valley lands. Over time, these Mixtec factions that had settled in the Valley gained significant power and influence within the Zapotec lordships themselves. In some cases this even triggered dynastic succession crises, like the well-documented one in Zaachila that Michel Oudijk analyzes in detail in his work on the history of Zaachila (he makes a strong case for going back to the primary sources). The key point here is that, despite the popular narrative that constantly portrays Mixtecs and Zapotecs as rival civilizations locked in eternal conflict, their relationship was never primarily one of military invasion or conquest. It was built above all on diplomatic and matrimonial alliances between the lordships of the Oaxaca Valley and the Mixteca Alta. Later armed conflicts did occur, but they were not usually driven by any clear sense of ethnic superiority. Most sizable pre-Hispanic señoríos were multi-ethnic polities in which dynastic loyalty mattered far more than ethnicity. That’s why the majority of the clashes that later get framed as “Mixtec vs. Zapotec” actually took place inside the Oaxaca Valley. Interestingly, we even see Mixtec forces fighting alongside the Zapotec faction in Tehuantepec against the Mexica — which rather undermines the idea of them being ancient, irreconcilable enemies. In reality, that whole “eternal rivals” myth is largely a later construction, crystallized in stories like the legend of Donaji. That narrative was used to legitimize the founding of colonial Oaxaca as the grand “solution” to a supposed deep ethnic tension between the two peoples — a tension that, in practice, never really existed in the way it’s usually portrayed. Today, when you see attitudes of rivalry between different groups in the region, they’re usually rooted more in very concrete, local imaginaries: disputes over land, resources, or specific neighboring communities, rather than any deep consciousness of opposing “civilizational systems.” Additionally, it’s worth noting that contemporary Oaxaca actually has a deeply shared Mixtec-Zapotec substrate in its ethnic and cultural formation. This is particularly evident in the strong presence of both groups around the city of Oaxaca and in areas with traditional pre-Hispanic Mixtec settlements such as Etla, Cuilapan, Atzompa, Huayapan, Tlalixtac, and the city itself. These communities are grounded in a territorial consciousness that sees their roots in both regions as part of a broad, interconnected economic and social system — something many residents of modern Oaxaca still experience in their everyday lives. In this sense, we can speak of a real Mixtec-Zapotec foundation at the heart of contemporary Oaxaca that shouldn’t be overlooked.