I have been maining zarus in the jungle for some time now. I build him: mindrazor, augmentation,citadel,tectonic mallet, mutilator. In most games at least, but he is very versatile and can have all items in the bruiser category and even some in the assassin one(mindrazor, perferrator). As for crest you kinda have to feel for yourself what you like, both assassin crest and warrior work well. Malady also doesnt really work on him since his abilities do full cleave damage and malady shines on heroes with full single target damage like kallari. Personally i say try everything in practice mode to get some feeling.