Will you stay at home --- (在.期间)the summer vacation?可以填durin

Will you stay at home ___ (在.期间)the summer vacation?可以填during吗?
There are three ___(零)in the number 168,000.为什么不能填zero,而要填复数zeroes?不是只有在...of中数字才用复数吗?（比如说hundreds of.）