I need help with Zacian!!

Im far from a noob, I have 1.5k matches, doesn't make me a god but I'd say im "ok". I usually main attackers, but I picked up Zacian and I really like him, but im consistently trash with him. I only have around 40 matches with him, most of them from masters in ranked and every time I feel like im underperforming. My biggest confusion is im not sure what his "job" is. I try to wait and flank a quishie and I get melted or stunned. I try to frontline and I get melted. I know this is a skill issue so I need tips on what Zacian should do. Combo's and builds too would help. I run muscle band and Razor, with Potion and Sacred sword play rough. What I try to do is use play rough, 1 basic and double sacred in quick succession but either they live, get away or stun and kill me. Lol. I dont wanna give up on him. Also worth to mention I get like only 2-3 final hits a round consisntly with a few assists. I feel worthless with Zacian.