How do I install Microsoft Equation 3.0 back to Office 365?

Polda18

Hello. I have an old document with equations in it and I need to edit them. The issue is, I can't because the old Microsoft Equation 3.0 isn't available anymore since 2018, so the only way to edit these equations is to actually convert them to the new format. That rises two issues. One is that the default font for new format equations is Cambria Math, while the document needs to use single font (Times New Roman) for the integrity and meet the requirements for sending document for review. The other is that new format supports only Math Type fonts, which by default is only Cambria Math, so I cannot set the equation to use Times New Roman font. I happen to have XITS Math font installed (which I had to install manually), it's almost exact copy of Times New Roman, with Math Type features in it. However, that doesn't actually solve it completely. If I screw up something in equations and need to edit it back, the controls of the new Equation Editor replace it back to Cambria Math, and also there is a bug in Equation Editor that inserts wrong unicode character for multiplication sign - it inserts a bullet instead of dot. It isn't noticeable with Cambria Math, because it uses the same glyph for both unicode characters so I never noticed before I used XITS Math, which happens to have the bullet correct size (large). That bug was non-present in Equation 3.0 and if you convert Equation 3.0 to the new format, change nothing in it, and only change the font to XITS Math, all characters are correct. Now, if I want to type in multiplication, I cannot use Equation Editor controls, I need to type in \cdot escape sequence to type in the correct glyph for multiplication sign.

I'd like to make things simple and use Equation 3.0 where I need to edit existing equations (which is pretty much every time). I am aware that it has a security hole, but I am quite sure that given that the AV software is capable of detecting such attack through that hole, given it's a known issue. I am using Avast Internet Security, paid licence.

Can I somehow add the Equation 3.0 back to Office 365? If so, how? Google isn't much helpful in this case