They aren't effected. Persona skills are always considered "ranged" attacks regardless of what they actually do. Bear in mind some physical skills may not be able to hit the back row in the first place, but that is a restriction on the skill not the skill user. Tons of persona physicals do "piercing" effects though which mean they hit the front row then a target in the back.
Also, yes, Zen uses a crossbow so he is ranged. He is also possibly a contender for hardest hitting straight physical attacker in the game which is all kinds of funny.
So using Chie in the front or Aigis in the back doesn't make a difference when it comes to skills? Cool. Although I guess now I'll need to figure out some other reason to choose either Chie or Aigis...
And if I do go with Aigis, I'm wondering if I should put her in the front row. She's got a ranged weapon, but she still looks like she could take hits even better than my current front row.