Why do I have to install onezipapp.exe to to download heidisql?

I tried to download the installer for version 12.13, but instead it wants me to install an entirely different application called onezipapp.exe. Why is this? I especially do not like the condition for dowload where it says "You agree that your default search engine will be changed as part of the installation." I do not like being told that I have to change my search engine. What has my choice of search engine got to do with heidisq? Why can't I download the software that I want instead of software which I don't want?

I have no clue what that onezipapp is, honestly. My guess is you accidentally clicked on an advertisement seen on the download page, and which looks like some download button. I highly recommend to uninstall that app if you already installed it, and instead have a look at the downloads in the latest Github release.

I have tried every link on that page called "download" and the result is always the same - instead of downloading heidisql I get a totally different application. It would appear that whatever software is being used to insert adverts into your download page it is converting EVERY download link. It is very confusing that those adverts are not clearly marked as adverts as there is no indication that they are NOT related to your software. I suggest you try this page for yourself and see what happens.

I currently cannot download the latest version of your software as all the download links have been hijacked.

I already pointed you to the right url with a link in my reply.

See the blue arrow in the following screenshot for which link to use for downloading:

I have nearly zero influence which ads are displayed there. Please understand the ads are generating me a small income for the otherwise free software.

That link may work now, but it didn't before. I tried every link on the page and got the same result - the wrong software.

If you click on a link labelled "download" and then try the link which you have highlighted you should see that it goes to the wrong place.