The Sun Stone? That is incredibly unlikely to have influenced the timeline.
While it is a powerful artifact, there are several problems with assuming that it could have changed the course of history. First, even if Porre found the 1000 AD "Sun Stone" (to note, Crono & Co used the 2300 AD Sun Stone), it wasn't really the Sun Stone. It was a partially charged Moon Stone. The question is if the Moon Stone is like a battery (partially charge it and you can use the charge even if it isn't full) or if it is like a nuclear reaction (it has to reach critical mass before it does anything fun).
Second, even assuming Porre obtained the Sun Stone, would they have even realized what it was capable of? People have known about lead for ages, but it was only after the discovery of radiation that we learned that lead is so good at blocking it. Likewise, oil was well known throughout much of human history, but only with the advent of the internal combustion engine was it even possible to apply oil for locomotive purposes.
Third, its primary purpose in Zeal (and even for Crono & Co) was as an Energy Source. Thus, in order to utilize it, Porre would have needed to have been able to extract that energy (plausible, as Lucca was able to do so with 1000 AD tech), but it would have also needed such exotic energy. Give a rural tribal village in Africa a nuclear power plant and they'll have access to more energy than they can imagine, but that doesn't suddenly turn them into a regional superpower. Energy Sources have one purpose; to provide power for those objects that require it. Before the Sun Stone could have influence Porre, Porre would need to have developed technology that required levels of Energy that only the Sun Stone could have practically provided. However, Porrean tech appears to be fairly primitive, on a near steam-punk level. Their energy needs do not seem to necessitate a power source like the Sun Stone.
Fourth, the secondary purpose of the Sun Stone is in its ability to form very nice alloys. Unfortunately, it appears that the only individual aware of this is Melchior. If Porre had Melchior working for them, then the Sun Stone becomes a moot point; Melchior is that influence outside the normal flow of time.
Zealean technology, on the other hand, is a very interesting possibility but I am afraid you haven't thought out the implications fully. Saying that Zealean technology is responsible for the rise of Porre is like saying that the answer to the question of "the chicken or the egg" is "coq au vin." The discovery of Zealean Technology must inherently occur after the influence that lead to the Rise of Porre, it cannot be that influence itself.
If Zealean technology was sufficient to change the course of history and cause the Rise of Porre,
then in the original timeline Porre must not have discovered it. The question is, then, what influenced Porre in such a manner that they discovered and began to unearth Zealean technology?
Zealean artifacts could be construed as foreign to the timeline, but they cannot satisfy Masato Kato's remarks; they are effects, not causes. There must be some other influence foreign to the original timeline that even led Porre to discover the Zealean Artifacts.
I am with Boo on this; the cause of the Rise of Porre must be in the rise of El Nido (though I disagree that Elements influenced that rise, as FATE would have been largely working against allowing those out into the wide world... unless Records of Fate accompanied Elements). But the very fact that El Nido existed shifted the political landscape significantly. In the pre-time-crash timeline, the Acacia Dragoons existed in the Porrean region at least up until around 1000 AD. In the post-time-crash timeline, the Acacia Dragoons moved to El Nido fairly early on. This left a power vacuum in the Porrean region, Porre could have then been able to expand, by expanding it might have gained access to sites where Zealean technology rested under the ground (such as the would-be site of Viper Manor, if only the Acacia Dragoons were still there to have built it).
Hmm okay they only appear in Home World. But Lucca says they don't exist in this timeline anymore.
I don't how to interpret that, did they die or did they just disappear from the Home World timeline?
And is Home World even a timeline itself?
Sort of. It appears that the Chronoverse is not a fractal multiverse. That is, every decision does not cause the universe to branch into two separate dimensions in which both decisions occur. Multiple dimensions seem to be able to exist, but the exact nature of these dimensions are difficult to determine (did they split from a single dimension or are they all unique from beginning to end and just happen to have similar elements?). But regardless, a timeline is the particular form that a single dimension takes. It is kind of like playdoh; the dimension is the playdoh itself, but the timeline is the shape that the playdoh has been molded into. If you change the timeline, the dimension remains the same, just as if you had made a bird out of playdoh but then changed it into a snake. The playdoh is still the same playdoh, but the shape has changed.
However, in CC, something went amiss. The Timeline was changed but instead of replacing the old one, it creates a new dimension. The one ball of playdoh somehow became two separate balls of playdoh, each with similar but different shapes.
