I want to say Parker wins a competitive decision but I have my doubts. Foreman isn't anything like Zhang or Wilder with a reactive defence, so all those feints will not make Foreman hesitate and allow Parker to control the pace of the fight. Foreman is more like Joyce a tank with a heavy jab and heavy, heavy hands who will try and walk Parker down and Parker now really doesn't use much movement preferring to fight on the edge of range. In the end I'm leaning towards Parker, simply because Foreman can't sustain enough work rate and pressure to win enough rounds and Parker has a good enough chin to take the odd big shot from Foreman to last the distance. Now 70's Foreman would be a completely different fight, prime Foreman batters Parker.
Parker has no head movement and goes back in straight lines He has been successful of late by virtue of being very active so is always in the gym and in good shape. One he plateaus and people figure out his patterns then his loss rate will pick up again. Old man Foreman was very wily and cunning.
Old man Foreman would be dangerous and his power exceeds Zhang’s imo and maybe even Wilder. However I think Parker is very crafty and his activity would allow him to take this one. A prime Foreman would be a different story and although I do rate the 40 plus year old version of him who was an immovable object, I think Parker would survive and win on points.