千头万绪 [- - wàn xù]a multitude of things; a host of miscellaneous problems; a multitude of things; a thousand and one things to attend to; thousands of strands and loose ends; extremely complicated and difficult to unravel; a thousand things to attend to; complexities of a situation:
•¶ 这个问题千头万绪， 三言两语说不清楚。 This problem is too complicated to be explained in a few words.
•¶千头万绪涌上心头。 A thousand confused thoughts come to one's mind.