Hey
@AFEX!
Here is the list that you wanted featuring Necrozma GX/Malamar! I'll explain some card choices below.
Necrozma GX/Malamar-------------------------------------------------------------------------------------------
****** Pokémon Trading Card Game Deck List ******
##Pokémon - 19
* 1 Oranguru SUM 113
* 2 Dawn Wings Necrozma-GX UPR 63
* 1 Espeon-EX BKP 52
* 4 Inkay FLI 50
* 1 Mew FCO 29
* 1 Mimikyu GRI 58
* 3 Necrozma-GX BUS 63
* 2 Tapu Lele-GX GRI 60
* 4 Malamar FLI 51
##Trainer Cards - 31
* 3 Float Stone BKT 137
* 3 Choice Band GRI 121
* 2 Cynthia UPR 119
* 3 Field Blower GRI 125
* 3 Guzma BUS 115
* 1 Lillie UPR 125
* 1 Max Potion GRI 128
* 4 Mysterious Treasure FLI 113
* 2 N FCO 105
* 4 Professor Sycamore BKP 107
* 4 Ultra Ball SUM 135
* 1 Super Rod BKT 149
##Energy - 10
* 10 Psychic Energy 5
Total Cards - 60
****** Deck List Generated by the Pokémon TCG Online
www.pokemon.com/TCGO ******
Card Choices-----------------------------------------------------------------------------------------------------------
Espeon EX (BKP): This is probably one of my best ideas for the deck, and I'm really confident in its usefulness. One of the differences between Ultra Necrozma GX and regular Necrozma GX is that the latter can use its GX move at any point (with the downside of it only effecting GX/EXs) while Ultra Necrozma GX has to wait until a total of six prizes remain in play (including your opponent's). Esepon EX and Black Ray GX are your best counter to Zoroark GX variants as you can hit them at any point you want (optimally when they have multiple Zoroark GX/GX partners such as Golisopod GX in play) and devolve them the next turn. Not to mention being able to search out Espeon EX with Mysterious Treasure as well.
Max Potion (GRI): I definitely don't think this card is necessary in the deck, but I thought that having one in wouldn't hurt and the synergy with Necrozma GX (since it discards all of it's energy after an attack) works pretty well. Another reason I put this in here is because I didn't know if you have any particular techs or wishes for the deck that I haven't included in my list, so Max Potion would probably be the first thing I (or you) would cut in order to include something else. It just makes things easier instead of mulling over what cards to take out.
Potential Techs--------------------------------------------------------------------------------------------------------
Professor's Letter (BKT): I'm personally not the biggest fan of this card when it comes to Malamar for just two reasons: One, it is another item for decks like Espeon GX/Garbodor (which this deck has trouble with anyways) to take advantage of which makes it even harder to maneuver yourself into a winning position. Two, You might as well play another Psychic Energy instead as it will make sure you have access to energy even late game (when most of your energy is in the discard pile). Now, I wouldn't mind playing one Professor's Letter, I personally just like to play more Energy, but you could always rearrange the numbers based upon your preference.
Altar of the Moone (GRI): I've been on the fence between Float Stone and Altar of the Moone for free retreat options, so I'm not particular sure which one is better. Float Stone means that you don't have to have an energy on Dawn Wings Necrozma GX, but Altar of the Moone allows you to bump opposing Stadiums (such as Parallel City which gives this deck some trouble) and lowers the Item count (to help against Esepon GX/Garbodor). It is really up to you, I don't know myself, but it would be something to test (which it would take a lot of in order to fully understand and I haven't gotten enough testing in to decide just yet).
Anyways, if you need anything else or have any questions, feel free to let me know!
Hope this helps!
~FrostBiter12