If your board and hand allows you to grow your Digimon in your nursery, stockpile at least +2000DP from inheritable effects: [ST1-01] Koromon and [ST1-03] Agumon grants +1000 DP each, while [BT5-009] Shoutmon and [BT1-015] Greymon grants +2000 DP each.
When properly stockpiled, your [BT5-017] Zeiggreymon will have at least 13000 DP during your turn. Depending on your opponent's board, you may choose to digivolve into Zeiggreymon inside your nursery, or outside if you wish to take advantage of his effect. With 13000 DP, he should survive a security attack or be able to take down an opponent's suspended Digimon.
If your opponent has a strong active Digimon you wish take down immediately, you can instead digivolve into [BT5-019] Shoutmon DX and by placing Zeiggreymon on top of your digivolution cards, allow you to direct your attack at your opponent's active Digimon.
[ST1-09] Metalgreymon ensures that your attack will not be blocked, as they would otherwise grant you with a hefty +3 memory and potentially swinging the turn back to you. If that happens, you can then digivolve into [BT5-086] Omnimon for another swing using .
[BT5-014] Omnishoutmon meanwhile grants you <SecurityAttack+1>, which is a rather rare asset in this deck since we mostly rely on inheritable effects that buff your DP. In addition, he also brings us additional warp digivolution robustness (from Shoutmon) since we run equal distributions of LV3/LV4/LV5/LV6.
Both Zeiggreymon and Omnishoutmon also serve as ammo for Shoutmon DX's [When Digivolving] effect, allowing him to delete an opponent's Digimon at 5000 DP or lower for each Zeiggrey/Omnishout you have in your digivolution cards. This allows your build to also be particularly effective against 5000 DP blockers and wide boards such as rookie rushes, Diaboromon, Crusadermon, and purple decks.