I have stayed in the Zambeze 2 times, in march and july 2011, along with some colleagues, in business trips to Tete.
Due to the flourishing coal mining business in Tete, Zambeze is almost all the time 100% booked, and it's very hard to get a room. Prices are the same as top quality Maputo hotels, but staff commitment to quality and good service is nearly none. The hotel is nicely placed and that's about it. Rooms are awful. Think in smoke smell, dirty sheets, pillows that smell like sweat. Leaking toilets. Bad reception small tube TVs, large and noisy A/Cs with no temperature control... You can expect bad infrastructure given you're in Tete, but dirty sheets and the uncommitted staff is truly unnacceptable. There were 2 times when my colleagues arrived, asked for the room and it was denied. After arguing for a while, the clerk gave them the room key that he originally wasn't planning to give. Breakfast and dinner aren't very good, but passable.
Don't come on tourism, unless you are the hardcore-style tourist or backpacker. If you are coming on business, bring clean sheets and some snacks, just in case.