See generally OCD(4) s.v. Zeno(1), by Malcolm Schofield; and web address 1 below. The present entry shows resemblences to a scholion on Plato, Alcibiades 119A, and esp. the Life of Zeno by Diogenes Laertius (9.25-29).
[1] In Italy; see under epsilon 768.
[2] 468-465 BCE. (Diogenes Laertius 9.29 says the 9th: 464-461 BCE.) Plato, Parmenides 127A, says that Zeno and his mentor Parmenides visited Athens for the Great Panathenaic festival at a time when Zeno was 'close to forty years old' and Socrates was 'very young.' Since Socrates' age at the time of his death is approximately known (slightly over 70) and the date of his execution is established (399 BCE), and since the Parmenides provides internal evidence as to the date of the visit (around 450 BCE), we can fix an exact date for Socrates' birth, and thereby a rough date for Zeno's, if we guess what Socrates' 'very young' age might have been. Based on this reckoning, Zeno's birth may be set sometime between 492 and 485 BCE (assuming that the 'very young' Socrates was between 18 and 25 at the time of Zeno's visit). On Pythagoras, see pi 3120, pi 3121, pi 3123, pi 3124; on Democritus, delta 447 & delta 448.
[3] Xenophanes of Colophon (xi 46) is often credited as a founder of Eleatic thought by ancient sources (e.g. Plato, Sophist 242C-D, and Aristotle, Metaphysics 1.5.986b). The evidence is unclear for this, but it is generally disbelieved by scholars nowadays. Evidence for association with Parmenides (pi 675) is much more reliable.
[4] It has been widely believed that Zeno wrote only one treatise: the one mentioned by Plato in the Parmenides. These titles mentioned in the Suda are therefore puzzling; the Interpretation of the Works of Empedocles is not mentioned anywhere else, and it has been suggested that what purport to be separate works are actually three different sections of one treatise (see Zeyl, 580).
[5] Diogenes Laertius 9.25 tells us that it was Aristotle who said this.
[6] So many versions of this story exist that precise details are probably impossible to ascertain. Diogenes Laertius 9.26 says that Zeno was arrested for shipping weaponry to Lipara and he offers three different versions of the tale: 1) that, when arrested, Zeno motioned to the tyrant that he wished to whisper something to him, and when the tyrant leaned in, Zeno bit his ear and did not let go until he was stabbed to death; 2) that he bit off the nose instead of the ear; and 3) just as the Suda describes, that Zeno gnawed off his own tongue and spat it upon the tyrant (an act which stirred the people up to such an extent that they stoned the tyrant to death). While perhaps containing a kernel of truth (Zeno's love for democracy and for his country is well-attested), this story probably should be assigned to the apocryphal biographies which abound for Presocratic philosophers (e.g. the tale of Heraclitus' death as a result of insulting and confusing his physicians, and of Empedocles' leap into the crater of Mt. Etna).
[7] Diogenes Laertius 9.28 offers this epitaph for Zeno (Greek Anthology 7.129): "you wished, o Zeno, and a noble thing it was for which you wished, to slay the tyrant / and free Elea from slavery. / Yet you were crushed, for the tyrant captured you and threw you in a mortar. / But what do I mean? Your body he beat, but not you."
[8] Again, see further under epsilon 768.