1. The sentence should be "Mehrdad and I went to the zoo." 2. If you really wanted to emphasize that _*you*_ were the one who did the job, you could say "I, myself, have done the job!" (you need those commas. The sentence does not work without them) is ok. "Myself" is working as an appositive. "I have done the job myself." would be more common.

"I myself" is used. It does not mean, however, that you did something by yourself. [looking at a video] Do people really jump off that cliff into the river below? Are they crazy? I myself did it last year. It's really fun and perfectly safe. [It's not just random other people that do it. I personally did it] I did the job myself. [This emphasizes that I did the job and not other people. Perhaps I was hoping that other people would do the job, but I ended up doing it] I did the job by myself. [This emphasizes that I didn't have any help doing the job. I knew that it was my responsibility to do the job, but I was hoping that others would give me some help. But I ended up being the only one who did it.]

It may be a bit awkward, but I have heard this expression in the UK quite often.

Jim and I went to the zoo (correct) Jim and me went to the zoo. (incorrect, but you will hear natives say this) Jim and myself went to the zoo. (also incorrect, but you could hear some natives say this if they were trying to sound rural.)

I want to emphasise that I have done it by myself! That is why I use this structure ''I myself...'' How to emphasise that ''I did the job myself''