Uthrows for lucario, and dthrows for zelda. Just up and grab em whenever you have the chance, and practice shielding their whole attacks. Zelda's usmash and fsmash are multi-hitbox attacks, so go into training and shield a perfectly aimed one of those, and count the times it hits your shield... Now you know how much you have to wait before attempting a grab, bair, utilt, or whatever else comes into mind... And for lucario, measure his fsmash range, and mindgame yourself into thinking that at high %s, he will mash fast aerials and smashes to kill you ASAP, and before you know it, you're shielding all his dairs and fsmashes.
They're tough, but they're not as tough as they're made out to be. Just keep the words "space" and "careful" alive in your mind, and the match should end up in your favor.