p.s. Here's the literal textbook example of how Armor is supposed to work with Mech Infantry, when in "Contact with an expected force", in Chapter 3 (Offensive Ops) from FM 71-1: Tank and Mechanized Infantry Company Team
The square symbology is for tanks, and the diamonds are your mech infantry. Mech Infantry's only job (all the way until the end) is to provide security on the flanks (Step 3) and getting into position, while its your tanks which are advancing on enemy BMPs. The Mech Infantry's engagement starts at Step 13 (the last step) when they are finally sent in to mop up the "remaining" resistance. And even that is still happening under the protection of your tanks (from Step 11).
The square symbology is for tanks, and the diamonds are your mech infantry. Mech Infantry's only job (all the way until the end) is to provide security on the flanks (Step 3) and getting into position, while its your tanks which are advancing on enemy BMPs. The Mech Infantry's engagement starts at Step 13 (the last step) when they are finally sent in to mop up the "remaining" resistance. And even that is still happening under the protection of your tanks (from Step 11).