通力合作: act with united strength; cooperate with a common effort; everybody pitching in for common work [a common task]; give full cooperation to ...; make a concerted [united] effort; pull well (
我保证通力合作: i can assuer you of our close cooperationi can assure you of our close cooperation
保持: (维持; 使不消失或减弱) keep; hold; retain; maintain; preserve 短语和例子保持安静 keep quiet; 保持优势 hold on to a dominant [favorable] position; 保持警惕 maintain vigilance; be on the alert; 保持清洁 keep clean; 保持优良传