Large multi criteria / Vlookup/Choose Multi criteria

HI all,

Hoping someone can help.

I have 2 formula's and need to make them match multiple criteria, currently sourcing from 1 column each.
In the attached file, column K is showing the largest value from column C. I would like to modify without a lengthy If statement that looks up the date in cell Z2 which would be on a diffrent tab in theory and then retrieves the corresponding column.

I could put =IF(Z2=W1,LARGE($C$2:$C$6,O2),IF(Z2=W2,LARGE($C$2:$C$6,O2))) etc, but that seems too long.

The 2nd formula I am really having trouble with is the Vlookup/Choose function. I am not sure how to, or if its possible to make that search the corresponding column dependant on which date is shown.

If anyone could help i would be very greatful!

Thanks