I'm going to assume you mean out of shield, as there's nothing stopping a Marth standing out of the range of shine from putting out a hitbox that will hit <spacie> on the basis of <spacie>'s inability to move enough out of the way if he's multi-shining.
Yes. If Shield DI is employed such that Marth ends up outside of the range of a second shine, he wins no questions asked.
The following assumes Marth does up-b OoS as fast as possible and did not powershield, and assumes the spacies execute their multishines as fast as possible without doing a double jump.
If Fox's shine is completely unstale, and starts from the ground, shield stun is over on the last frame of jumpsquat, so Marth would have just begun his jump out of shield, and could cancel on the next frame. But, shine can also come out on the frame he'd be cancelling the jump OoS. So frame 1 of shine would match up to frame 1 of up-b here.
I Fox was airborne, as in had already done two shines, he has to wait an additional 2 frames before jumping to become grounded and not end the multi-shine cycle, so shine's hitbox is out frame 3 of dolphin slash. He'd still need another two frames before a hitbox comes out (and the move's own invincibility).
Stale Fox's shine once, goes from 5 to about 4 percent, losing and entire frame of stun. Stale it twice more, and it's at 3 percent. Continue staling beyond that and you'll eventually end up under 3 percent, at which point Marth's Up-B will win vs continued multishines after two.
Switch to Falco, and when completely unstale, there's 1 more frame they're out of stun between shines, but 1 less for anything involving cancelling jump-squat. Staling will take longer to reduce stun, but when completely unstale, the move does just over 4 and 1/3 percent, so it will give Marth enough time to dolphin slash after 2 shines.
