Sweet Corn and Zinnia
Beneficial Pair — Good Match
That corn is wind-pollinated and doesn't support pollinators on its own is simply a fact about the plant, not a claim requiring evidence. Whether adding zinnia nearby measurably benefits corn's own yield is a different question - it doesn't, directly, since corn doesn't need insect pollination. The real benefit is to the wider garden's pollinator activity, which is a real but indirect effect rather than a corn-specific one.
Mechanism: Pollinator / Beneficial-Insect Attraction
Sweet corn is wind-pollinated and doesn't rely on or attract insect pollinators at all, which means a corn block on its own offers nothing to support the bee and beneficial-insect populations that neighboring crops in a mixed garden may depend on. Zinnia, planted at the edge of a corn block, fills that gap with a long, continuous bloom season that draws pollinators and predatory insects into the same general area, indirectly supporting whatever insect-pollinated crops are growing nearby.
This pairing is a little different from most on this site, because sweet corn itself gets no direct benefit from zinnia - corn is wind-pollinated and simply doesn't interact with flowering companions the way a bee-dependent crop like squash or watermelon does.
The Benefit Runs to the Garden, Not to the Corn
Really, this pairing is garden-wide pollinator support dressed up as a corn companion: a corn block offers nothing to visiting bees, so a zinnia border nearby helps keep pollinator activity high in that part of the garden for whatever else you're growing close by that does depend on insect pollination, whether that's the same bed's squash or a neighboring row of beans.
Spacing
Zinnia's spacing is flexible, from 6 to 18 inches depending on variety, which makes it easy to tuck along a corn block's border without competing for the tight 12-18 inch spacing corn needs within its own rows for reliable wind pollination.
Watch For
Corn planted in a single thin row rather than a block pollinates poorly regardless of what's planted nearby, since wind pollination depends on pollen from many plants reaching many silks in close proximity - this is worth fixing before worrying about zinnia or any other companion, since it affects corn's own yield far more directly.
Frequently Asked Questions
Does it matter which side of the corn block I plant zinnia on?
Less than it would for a true trap-crop pairing, since zinnia isn't intercepting anything approaching the corn - it's simply adding pollinator activity to the general area. A border sited toward whichever side is closest to other insect-pollinated crops you're growing puts that benefit where it's actually useful, rather than facing it toward a fence or another wind-pollinated planting that won't use it.