Zillions of Games is highly optimised for Chesslike games -- in particular Chess itself! -- whereas Ludii is designed to support a wider range of games. Compare Zillions and Ludii at Hex. Or Taikyoku Shogi.
Zillions uses a number of clever optimisations that make it work well for Chess and Chesslike games. For example, the Chess board is 8x8 = 64 cells, which Zillions exploits by using bitboards (i.e. the entire board represented by a single 64-bit long integer). These allow highly efficient encoding of game states and other useful data such as attack tables, positional tables, etc. The Ludii game states also uses bitwise encoding but in a more general format that includes additional information; there are about a dozen different state types to handle the wider range of games.
Ludii's primary purpose is as a game design and analysis tool. AI playing strength is of secondary concern, provided that the AI plays at a sufficient level to allow useful anlayses.
Zillions uses a number of clever optimisations that make it work well for Chess and Chesslike games. For example, the Chess board is 8x8 = 64 cells, which Zillions exploits by using bitboards (i.e. the entire board represented by a single 64-bit long integer). These allow highly efficient encoding of game states and other useful data such as attack tables, positional tables, etc. The Ludii game states also uses bitwise encoding but in a more general format that includes additional information; there are about a dozen different state types to handle the wider range of games.
Ludii's primary purpose is as a game design and analysis tool. AI playing strength is of secondary concern, provided that the AI plays at a sufficient level to allow useful anlayses.