Napoleonic Warlord are at the larger end of 28mm. I have them mixed in with Victrix plastic, Perry Plastic and metal, Front Rank metal, and some Casting Room metals (in my opinion the only ones noticeably smaller) without too many problems.
If I remember this correctly 28mm is nominally 1/56th scale (Yes I know sizes in mm are technically not a scale
) and the Zvezda models are 1/72nd?
Tony.
Edit in Italics