The fan oven element may have failed as well if someone insisted on keep on trying the oven without the fan running.
Replacing the fan is reasonably easy. I'm not going to search for and repeat instructions you can find for yourself. Just do a Google search for "replace zanussi oven fan" or similar. Do just watch out for tricky fans to remove frm the motor shaft; sometimes they are secured with a left hand thread nut and, no matter how many times I do it, undoing a nut by rotating it clockwise feels just plain wrong.
Ditto the fan oven element, really. Just do Google searches for "check fan oven element" and ""replace Zanussi fan oven element" or similar.
Wotk methodically, take notes on paper - do not rely on memory.
And Think.
Acp, August 2017