CLS team should be able to take Bossk. Assuming CLS Han Chewie, open stun on bossk, kill boba twice while using stuns/CLS special to stop bossk from taking a turn. Should be an easy go from there
For GK/Zarris, you should be able to get someone to stack damage (Yolo, FOE, Wampa, (maybe Nest?)) and eventually just totally demolish the two of them. If the third guy is a threat you might need to take someone to suppress him, but in general you can just boost your damage stacker. Guys like FOO and Jyn work great. I'd imagine armor shred would be useful too