11:18 Oct 21, 2011 

This is the problem with English - there are often no cut and dried rules and there are always grey areas. The definite article makes a big difference. "Last year I have worked" is never correct ;-) as by definition last year is finished. "The last year" could mean the last calendar year (i.e. finished) or the last 12 months (up to today i.e. unfinished). So, if you want to talk of one job, there could be confusion. However, you want to talk of two jobs and I think that makes it clearer. "During the last/past year I have worked as A and B" - well, nothing's really sure: 2 ongoing part-time? 1 finished, 1 ongoing? 2 finished? In a job application, the obvious answer would be the last. Leave it to the reader!

10:54 Oct 21, 2011 

I will add an example so to let you all better evaluate.
Last (past) year I have worked as X from january to may and then as Y from july to october and now I am unemployed and applying for Z, a position that has some skills in common with both X and Y and thus i would like to underline that.
Thanks for your efforts