Because Jeleva, Nephalia's Scourge let's you cast the spells any relevant cast triggers will trigger. This includes Mirari. Not that Mirari copies the spell, not casts it, so you will technically only be casting the spell once for any other relevant on cast triggers (like storm), but you will have two copies of the spell, so in this case you'd get 26 zombies.
March 12, 2018 12:13 a.m.
706.10. To copy a spell, activated ability, or triggered ability means to put a copy of it onto the stack; acopy of a spell isnt cast and a copy of an activated ability isnt activated. A copy of a spell orability copies both the characteristics of the spell or ability and all decisions made for it, includingmodes, targets, the value of X, and additional or alternative costs. (See rule 601, Casting Spells.)Choices that are normally made on resolution are not copied. If an effect of the copy refers toobjects used to pay its costs, it uses the objects used to pay the costs of the original spell or ability.A copy of a spell is owned by the player under whose control it was put on the stack. A copy of aspell or ability is controlled by the player under whose control it was put on the stack. A copy of aspell is itself a spell, even though it has no spell card associated with it. A copy of an ability is itselfan ability.