I'm in WI too You've actually missed the prime time for moving lilacs this spring. Oct. would be the next time for 'by-the-book' transplanting. But, nothing ventured, nothing gained! You may wish to try what the previous poster recommended. Good luck with your lilacs!
Lilacs are very hardy. Best to wait until after it has flowered and finished. When digging it up, try to leave a good "ball" of soil around the roots of the lilac, and make sure the new hole is roomy enough to place it in. When you have backfilled the hole, healed in the lilac, water really well, and water daily for 2 weeks. Your lilac should be just fine. Good luck and happy gardening.
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