lol thats the second time I've heard something like "OLIMAR SPAMZ PIKMIN OMG HE IS SOOOO BROKEN AND CHEEP" Olimar has about six attacks without Pikmin, what else is he supposed to do? anyway sorry for the Flame, being an Olimar main I could probably help. My strategy is to throw the Pikmin, and when my opponent attacks to get the Pikmin off I run in for a grab, or a Dash A to lead into a combo, you seem to have the idea down of letting the Pikmin stay on and attacking Olimar while getting the Pikmin off at the same time.
That would work for a while but once the player realizes they aren't easily going to get away with throw pikmin, attack their play style will begin to change. I think Zamus's Neutral B, the gun, can reflect Pikmin so try using that to keep Pikmin away. I'm not sure about Grab Ranges but I think Zamus's tether like grab thing is longer then some of Olimars grabs (ZOMG BROKEN GRAB NUB) This does seem like a bit of a tough match up for Zamus because Olimar easily out camps her. Zamus has a tether recovery too, so doesn't hers suck just as much as Olimar :| Olimars is probably better because he can do more to stop it =\
I noticed that most of the time just doing one jab can get Pikmin off of Zamus, so just do a quick jab to get them off, maybe take advantage of your gun more often to kill off his Pikmin once they've been thrown at you and go at him when he plucks more.
But I don't know a lot about Zero Suit Samus, and have never really fought any with my Olimar so I don't really know much about this match up but I hope I helped anyway.