Just to add, though it's been a while so take my vague recollections for what they are, but: The Mexican state was forced to acknowledge and negotiate (when they previously had refused) only because of some long-standing international war treaty that obliges member states to open negotiations with belligerent war parties - something a state wouldn't ever consider with, let's say, a random group of activists of whatever color (usually, they simply pretend to listen, never negotiate on even ground - because the ground isn't even). The way I see it, the initial declaration of war serves as a milestone of both internal coherence and legitimization towards larger governmental bodies. This in turn forces these bodies to negotiate, which further legitimizes the belligerent faction.

But also, never forget how they organized in secret for about a decade before ever making that declaration of war.