I like him as a player but he doesn't provide a lot of width or pace. I see him as more similar to Eriksen or Fernandes than to Sancho. Wouldn't have a problem if he came but we have alarming issues in midfield, at right back and up front. I don't see Ziyech solving any of those.
IMO our current single biggest issue is winger depth. You need 3 top wingers to rotate and compete with each other. Especially with 5 subs this season. They push each other on and rotate when one gets bad form or injured. So that should be #1 priority. Elanga is currently that player for us, and he isn't a premier league level footballer for me. So if one goes down, we resort to playing players out of position or using a championship level player.
Up top yes we have issues, but if we do nothing, we at least have martial and Ronaldo to rotate between and Rashford who can slot in if we're desperate. At right back it's not ideal, but dalot is decent and I think ten hag clearly likes him, and Wan Bissaka as backup is fine. Midfield 3 we have 6 decent to good players (and all certainly would be wanted by top half premier league sides in some capacity). So again. Not as good as we want, but far more prepared to go through a premier league season.