MTGNexus

If I have Jaya, Venerated Firemage and Jeska, Thrice Reborn in play, can I activate Jeska for -x as zero and "deal" zero damage up to 3 different targets and then Jaya would add an additional plus 1 to those 3 targets, therefore dealing 1 damage to each target?

The wording on Jaya says "If another red source you control would deal damage to a permanent or player" so it then becomes a case of is dealing zero damage considered dealing damage?

No, zero damage is indeed no damage at all. You can't replace an event that does not happen with Jaya.

Jeska doesn't distribute damage in the way Pyrotechnics for example does. Her loyalty ability deals the same (X) damage to each target.