'She is the woman whom we employed last year.'
But according to Wren nd Martin:
'He was the man who (not whom) they determined should be the next mayor.'
It is actually clear which one we should believe, but then the problem is its not possible to compare always. And what will happen when we do practice tests. I am confused.
What do u think guys.
Dude, these two usages are completely different, even thought they might seem the same at first glance. The verbs used here are different, look..
EMPLOYED
DETERMINED
In the first usage, you can make do even without using the "whom", i.e., "She is the woman we employed last month"
In the second usage, look at it this way and see which would be a better option - "He was the man they determined should be the next mayor"
I don't read much of Wren and Martin (OR CL or TIME material

), but this is what my intuition tells me.
Also tell me the answers for these,
'I will vote for whoever/whomever you suggest.'
'It was she/her at the window'
'If you were I/me, would you accept the job?'
I will vote for whomever you suggest.
It was her at the window.
If you were me, would you accept the job?
(not dead sure, but this is what I would've marked in CAT)